2020 Day 12
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2020/12/README.md
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2020/12/README.md
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# 2020 Day 12: Rain Risk
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#### [Direct Link](https://adventofcode.com/2020/day/12)
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## Part 1
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Your ferry made decent progress toward the island, but the storm came in faster than anyone expected. The ferry needs to take **evasive actions**!
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Unfortunately, the ship's navigation computer seems to be malfunctioning; rather than giving a route directly to safety, it produced extremely circuitous instructions. When the captain uses the [PA system](https://en.wikipedia.org/wiki/Public_address_system) to ask if anyone can help, you quickly volunteer.
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The navigation instructions (your puzzle input) consists of a sequence of single-character **actions** paired with integer input **values**. After staring at them for a few minutes, you work out what they probably mean:
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- Action **`N`** means to move **north** by the given value.
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- Action **`S`** means to move **south** by the given value.
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- Action **`E`** means to move **east** by the given value.
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- Action **`W`** means to move **west** by the given value.
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- Action **`L`** means to turn **left** the given number of degrees.
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- Action **`R`** means to turn **right** the given number of degrees.
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- Action **`F`** means to move **forward** by the given value in the direction the ship is currently facing.
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The ship starts by facing **east**. Only the `L` and `R` actions change the direction the ship is facing. (That is, if the ship is facing east and the next instruction is `N10`, the ship would move north 10 units, but would still move east if the following action were `F`.)
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For example:
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```
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F10
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N3
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F7
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R90
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F11
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```
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These instructions would be handled as follows:
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- `F10` would move the ship 10 units east (because the ship starts by facing east) to **east 10, north 0**.
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- `N3` would move the ship 3 units north to **east 10, north 3**.
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- `F7` would move the ship another 7 units east (because the ship is still facing east) to **east 17, north 3**.
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- `R90` would cause the ship to turn right by 90 degrees and face south; it remains at **east 17, north 3**.
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- `F11` would move the ship 11 units south to **east 17, south 8**.
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At the end of these instructions, the ship's [Manhattan distance](https://en.wikipedia.org/wiki/Manhattan_distance) (sum of the absolute values of its east/west position and its north/south position) from its starting position is `17 + 8` = **`25`**.
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Figure out where the navigation instructions lead. **What is the Manhattan distance between that location and the ship's starting position?**
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## Part 2
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Before you can give the destination to the captain, you realize that the actual action meanings were printed on the back of the instructions the whole time.
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Almost all of the actions indicate how to move a **waypoint** which is relative to the ship's position:
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- Action **`N`** means to move the waypoint **north** by the given value.
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- Action **`S`** means to move the waypoint **south** by the given value.
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- Action **`E`** means to move the waypoint **east** by the given value.
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- Action **`W`** means to move the waypoint **west** by the given value.
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- Action **`L`** means to rotate the waypoint around the ship **left** (**counter-clockwise**) the given number of degrees.
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- Action **`R`** means to rotate the waypoint around the ship **right** (**clockwise**) the given number of degrees.
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- Action **`F`** means to move **forward** to the waypoint a number of times equal to the given value.
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The waypoint starts **10 units east and 1 unit north** relative to the ship. The waypoint is relative to the ship; that is, if the ship moves, the waypoint moves with it.
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For example, using the same instructions as above:
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- `F10` moves the ship to the waypoint 10 times (a total of **100 units east and 10 units north**), leaving the ship at **east 100, north 10**. The waypoint stays 10 units east and 1 unit north of the ship.
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- `N3` moves the waypoint 3 units north to **10 units east and 4 units north of the ship**. The ship remains at **east 100, north 10**.
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- `F7` moves the ship to the waypoint 7 times (a total of **70 units east and 28 units north**), leaving the ship at **east 170, north 38**. The waypoint stays 10 units east and 4 units north of the ship.
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- `R90` rotates the waypoint around the ship clockwise 90 degrees, moving it to **4 units east and 10 units south of the ship**. The ship remains at **east 170, north 38**.
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- `F11` moves the ship to the waypoint 11 times (a total of **44 units east and 110 units south**), leaving the ship at **east 214, south 72**. The waypoint stays 4 units east and 10 units south of the ship.
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After these operations, the ship's Manhattan distance from its starting position is `214 + 72` = **`286`**.
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Figure out where the navigation instructions actually lead. **What is the Manhattan distance between that location and the ship's starting position?**
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63
2020/12/code.py
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2020/12/code.py
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# SPDX-License-Identifier: MIT
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# Copyright (c) 2020 Akumatic
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#
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#https://adventofcode.com/2020/day/12
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def readFile() -> list:
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with open(f"{__file__.rstrip('code.py')}input.txt", "r") as f:
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return [line.strip() for line in f.readlines()]
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def part1(input: list) -> int:
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x, y = 0, 0
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dirs = ((1,0), (0, 1), (-1, 0), (0, -1))
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idx = 0
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for instruction in input:
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action = instruction[0]
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value = int(instruction[1:])
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if action == "N":
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y += value
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elif action == "S":
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y -= value
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elif action == "E":
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x += value
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elif action == "W":
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x -= value
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elif action == "F":
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x += dirs[idx][0] * value
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y += dirs[idx][1] * value
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else: # action in ("R", "L")
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sig = 1 if action == "L" else -1
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idx = (idx + sig * value // 90) % 4
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return abs(x) + abs(y)
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def part2(input: list) -> int:
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x, y, wx, wy = 0, 0, 10, 1
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dirs = ((1,1), (-1, 1), (-1, -1), (1, -1))
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idx = 0
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for instruction in input:
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action = instruction[0]
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value = int(instruction[1:])
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if action == "N":
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wy += value
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elif action == "S":
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wy -= value
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elif action == "E":
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wx += value
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elif action == "W":
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wx -= value
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elif action == "F":
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x += wx * value
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y += wy * value
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else: # action in ("R", "L")
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sig = 1 if action == "L" else -1
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for _ in range(value // 90):
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idx_prev, idx = idx, (idx + sig) % 4
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tmp_wx = wx
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wx = wy * dirs[idx_prev][1] * dirs[idx][0]
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wy = tmp_wx * dirs[idx_prev][0] * dirs[idx][1]
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return abs(x) + abs(y)
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if __name__ == "__main__":
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input = readFile()
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print(f"Part 1: {part1(input)}")
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print(f"Part 2: {part2(input)}")
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776
2020/12/input.txt
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2020/12/input.txt
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R180
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E1
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N1
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R90
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E4
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F84
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W3
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F19
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E5
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N1
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W5
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W4
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R90
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S1
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F70
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R90
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W2
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S3
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L180
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E2
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R90
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E1
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R90
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N2
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E3
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F55
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W3
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R90
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S2
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E4
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L90
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F33
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W4
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S3
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F11
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N4
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W4
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F88
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W3
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F62
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L90
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S3
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W3
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N1
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E3
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E2
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N1
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E3
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S3
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E5
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S4
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W5
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L90
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W5
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R90
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E4
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F36
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N4
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E4
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E5
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F47
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R90
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N3
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E3
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L180
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S5
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R90
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S5
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W2
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S3
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F43
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W2
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R180
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W2
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S2
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L180
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E2
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F49
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L90
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F77
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S5
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E1
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S2
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F39
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L180
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F12
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W1
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L90
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F60
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S2
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E3
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N1
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E5
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R90
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E1
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N4
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W4
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S4
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E2
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L90
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F100
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E3
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F58
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S2
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E4
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F83
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W3
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N1
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R90
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F99
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W5
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W4
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F19
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N3
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W1
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W5
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F70
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R180
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R90
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F58
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E5
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N3
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R90
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N4
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F86
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N4
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F70
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L90
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F36
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R90
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S4
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R180
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N5
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F81
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W5
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R90
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E5
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L90
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F73
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S5
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E3
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N1
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F27
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E2
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N3
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L180
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W2
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F24
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N2
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L90
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F69
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N2
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E3
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F49
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L90
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S4
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W5
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F18
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R180
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F62
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S2
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F65
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E3
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F100
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N1
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F96
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W1
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F75
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L180
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W2
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S2
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F93
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E5
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S3
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R90
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S2
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F34
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R90
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F83
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S1
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W1
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F58
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L180
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N4
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E1
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R90
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W2
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F93
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S3
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F20
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R90
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N3
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E3
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N3
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L90
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F8
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S3
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F18
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S3
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N2
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F6
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L270
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F70
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W5
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S3
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F54
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E2
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F75
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E3
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R90
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N2
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W3
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L90
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E4
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F58
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N5
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F97
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W2
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L90
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W5
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S2
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W1
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S5
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F85
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N1
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E1
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N4
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E4
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L90
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E1
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R90
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S5
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L180
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R270
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N1
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L90
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E4
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N3
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F45
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N2
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F68
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R90
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F36
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N5
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F82
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S5
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E4
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R180
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S2
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L180
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N3
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R270
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W5
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F70
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L90
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W5
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F80
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W4
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N2
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R90
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S3
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W1
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F23
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N1
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W1
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N4
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F70
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S3
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L180
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F57
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R90
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L90
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F55
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L90
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N4
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F87
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L90
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F1
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L270
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F17
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N5
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R180
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F84
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R90
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W5
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F7
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W1
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S1
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E3
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F46
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S5
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E2
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F23
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R90
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E4
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W2
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F96
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E5
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L90
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F65
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F3
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S5
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E5
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N3
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W4
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L90
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S2
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F57
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E1
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R90
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F68
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E3
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L90
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W1
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F29
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N5
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W5
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N1
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F95
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N1
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L90
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F31
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S5
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L180
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N2
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W5
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R90
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F27
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E1
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R90
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E3
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S5
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F10
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R90
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N4
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E2
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F25
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S4
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E5
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F51
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N3
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W2
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L90
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S3
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L180
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F17
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E4
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F93
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E3
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L90
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F41
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L90
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S5
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L90
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W5
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N1
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F81
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L90
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E4
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W2
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R90
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W1
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S5
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R90
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F39
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W3
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R90
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N5
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E1
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L90
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F82
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S3
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R90
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W4
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F66
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F4
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L90
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F77
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R90
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E1
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L90
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F53
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S4
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F35
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W1
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F64
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R90
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F9
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S1
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E1
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L90
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W4
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R90
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S2
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W5
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R90
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S4
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L90
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N3
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F8
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L180
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N5
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E5
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N4
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F35
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N5
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W1
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N1
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E5
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F15
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R180
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F92
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W3
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L90
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F4
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L90
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E1
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S3
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W3
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R90
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F37
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N5
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F19
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S2
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F98
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L90
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F24
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W3
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F68
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N5
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R90
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W3
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L90
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W3
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L90
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S1
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L90
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S4
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W3
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F56
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N4
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R90
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E3
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W1
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L90
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E4
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N3
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R180
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E1
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S1
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W2
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R90
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N3
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F82
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N2
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F37
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S3
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L180
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E2
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L180
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F6
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N2
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F96
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E2
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R180
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E2
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W3
|
||||
R90
|
||||
E2
|
||||
S5
|
||||
S1
|
||||
F23
|
||||
R90
|
||||
W5
|
||||
F75
|
||||
S1
|
||||
L90
|
||||
S3
|
||||
E1
|
||||
F83
|
||||
W4
|
||||
L180
|
||||
W5
|
||||
L90
|
||||
N1
|
||||
E1
|
||||
S2
|
||||
F17
|
||||
L90
|
||||
S2
|
||||
F53
|
||||
R90
|
||||
S3
|
||||
N3
|
||||
W1
|
||||
N4
|
||||
L180
|
||||
L90
|
||||
E3
|
||||
F9
|
||||
S5
|
||||
F24
|
||||
W3
|
||||
E5
|
||||
N2
|
||||
F73
|
||||
N1
|
||||
F28
|
||||
N2
|
||||
W4
|
||||
N3
|
||||
F53
|
||||
E5
|
||||
F47
|
||||
W2
|
||||
F60
|
||||
L90
|
||||
E2
|
||||
F19
|
||||
S1
|
||||
F63
|
||||
W5
|
||||
F100
|
||||
N3
|
||||
L180
|
||||
F83
|
||||
N4
|
||||
W5
|
||||
F37
|
||||
S1
|
||||
F50
|
||||
E1
|
||||
N2
|
||||
W3
|
||||
R90
|
||||
F85
|
||||
S4
|
||||
F72
|
||||
N4
|
||||
L90
|
||||
F48
|
||||
R90
|
||||
F99
|
||||
R90
|
||||
F58
|
||||
W3
|
||||
W4
|
||||
F64
|
||||
E1
|
||||
R90
|
||||
F74
|
||||
L90
|
||||
F23
|
||||
N3
|
||||
N3
|
||||
E1
|
||||
S1
|
||||
W5
|
||||
L180
|
||||
F98
|
||||
L90
|
||||
F36
|
||||
W4
|
||||
S2
|
||||
W3
|
||||
F9
|
||||
F72
|
||||
W5
|
||||
F78
|
||||
N2
|
||||
F65
|
||||
S3
|
||||
F47
|
||||
S5
|
||||
R90
|
||||
F68
|
||||
L180
|
||||
W2
|
||||
F7
|
||||
E2
|
||||
E3
|
||||
S4
|
||||
R90
|
||||
N2
|
||||
L180
|
||||
W2
|
||||
R180
|
||||
E4
|
||||
R90
|
||||
W3
|
||||
L90
|
||||
E4
|
||||
F54
|
||||
L180
|
||||
E2
|
||||
F6
|
||||
W5
|
||||
F82
|
||||
E4
|
||||
R90
|
||||
E4
|
||||
F25
|
||||
N2
|
||||
R270
|
||||
N4
|
||||
F18
|
||||
N5
|
||||
R90
|
||||
S3
|
||||
R90
|
||||
F38
|
||||
R90
|
||||
F97
|
||||
W4
|
||||
F85
|
||||
S4
|
||||
F56
|
||||
E4
|
||||
S1
|
||||
F40
|
||||
W3
|
||||
F52
|
||||
L90
|
||||
F76
|
||||
N4
|
||||
F15
|
||||
S2
|
||||
F22
|
||||
S5
|
||||
L180
|
||||
F91
|
||||
L180
|
||||
F8
|
||||
L90
|
||||
E4
|
||||
N4
|
||||
F67
|
||||
L90
|
||||
S3
|
||||
R180
|
||||
R90
|
||||
N4
|
||||
F71
|
||||
W3
|
||||
F34
|
||||
E2
|
||||
N1
|
||||
F43
|
||||
W5
|
||||
L180
|
||||
N5
|
||||
W2
|
||||
F42
|
||||
R90
|
||||
W3
|
||||
F39
|
||||
E1
|
||||
S2
|
||||
L180
|
||||
N5
|
||||
E3
|
||||
N5
|
||||
F28
|
||||
E1
|
||||
R90
|
||||
S3
|
||||
F40
|
||||
L90
|
||||
S2
|
||||
S2
|
||||
L90
|
||||
W5
|
||||
L90
|
||||
F93
|
||||
R180
|
||||
W4
|
||||
S4
|
||||
W4
|
||||
F100
|
||||
S3
|
||||
R90
|
||||
E2
|
||||
L180
|
||||
W1
|
||||
E3
|
||||
S5
|
||||
L90
|
||||
F87
|
||||
N1
|
||||
R90
|
||||
F3
|
||||
R90
|
||||
E5
|
||||
R90
|
||||
S3
|
||||
F45
|
||||
L90
|
||||
S2
|
||||
F42
|
||||
R90
|
||||
F95
|
||||
L90
|
||||
E1
|
||||
N3
|
||||
R90
|
||||
F73
|
||||
S3
|
||||
E1
|
||||
L90
|
||||
S2
|
||||
E3
|
||||
L90
|
||||
L270
|
||||
F38
|
||||
S5
|
||||
R90
|
||||
F42
|
||||
L90
|
||||
N1
|
||||
F7
|
||||
S3
|
||||
F65
|
||||
N2
|
||||
F42
|
||||
L180
|
||||
W5
|
||||
S4
|
||||
E4
|
||||
F65
|
||||
S4
|
||||
E5
|
||||
F51
|
||||
E4
|
||||
R180
|
||||
F70
|
||||
R90
|
||||
F28
|
||||
N5
|
||||
W5
|
||||
N1
|
||||
F96
|
||||
L90
|
||||
W4
|
||||
S3
|
||||
W3
|
||||
F89
|
||||
W1
|
||||
L90
|
||||
F75
|
||||
L270
|
||||
S3
|
||||
R90
|
||||
L90
|
||||
F7
|
||||
E2
|
||||
F24
|
||||
R180
|
||||
S2
|
||||
L180
|
||||
F48
|
||||
R90
|
||||
F37
|
||||
W2
|
||||
R90
|
||||
W4
|
||||
L90
|
||||
W3
|
||||
F81
|
||||
E4
|
||||
N2
|
||||
F39
|
||||
E4
|
||||
N1
|
||||
W1
|
||||
L90
|
||||
F59
|
||||
2
2020/12/solution.txt
Normal file
2
2020/12/solution.txt
Normal file
@ -0,0 +1,2 @@
|
||||
Part 1: 1424
|
||||
Part 2: 63447
|
||||
13
2020/12/test_code.py
Normal file
13
2020/12/test_code.py
Normal file
@ -0,0 +1,13 @@
|
||||
# SPDX-License-Identifier: MIT
|
||||
# Copyright (c) 2020 Akumatic
|
||||
|
||||
from code import part1, part2
|
||||
|
||||
def test():
|
||||
input = ["F10","N3","F7","R90","F11"]
|
||||
assert part1(input) == 25
|
||||
assert part2(input) == 286
|
||||
print("Passed tests for", input)
|
||||
|
||||
if __name__ == "__main__":
|
||||
test()
|
||||
@ -20,7 +20,7 @@ Collect stars by solving puzzles. Two puzzles will be made available on each day
|
||||
| 05 | :white_check_mark: | :white_check_mark: || 06 | :white_check_mark: | :white_check_mark: |
|
||||
| 07 | :white_check_mark: | :white_check_mark: || 08 | :white_check_mark: | :white_check_mark: |
|
||||
| 09 | :white_check_mark: | :white_check_mark: || 10 | :white_check_mark: | :white_check_mark: |
|
||||
| 11 | :white_check_mark: | :white_check_mark: || 12 | | |
|
||||
| 11 | :white_check_mark: | :white_check_mark: || 12 | :white_check_mark: | :white_check_mark: |
|
||||
| 13 | | || 14 | | |
|
||||
| 15 | | || 16 | | |
|
||||
| 17 | | || 18 | | |
|
||||
|
||||
Loading…
x
Reference in New Issue
Block a user