AtCoder Grand Contest 033
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Problem Statement
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Takahashi and Aoki will play a game on a tree. The tree has $N$ vertices numbered $1$ to $N$, and the $i$-th of the $N-1$ edges connects Vertex $a_i$ and Vertex $b_i$.
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At the beginning of the game, each vertex contains a coin. Starting from Takahashi, he and Aoki will alternately perform the following operation:
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- Choose a vertex
$v$that contains one or more coins, and remove all the coins from$v$. - Then, move each coin remaining on the tree to the vertex that is nearest to
$v$among the adjacent vertices of the coin's current vertex.
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The player who becomes unable to play, loses the game. That is, the player who takes his turn when there is no coin remaining on the tree, loses the game. Determine the winner of the game when both players play optimally.
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Constraints
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$1 \leq N \leq 2 \times 10^5$$1 \leq a_i, b_i \leq N$$a_i \neq b_i$- The graph given as input is a tree.
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Input
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Input is given from Standard Input in the following format:
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N
a_1 b_1
a_2 b_2
:
a_{N-1} b_{N-1}
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Output
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Print First if Takahashi will win, and print Second if Aoki will win.
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样例
Input #1
3
1 2
2 3
Output #1
First
Here is one possible progress of the game:
- Takahashi removes the coin from Vertex $1$. Now, Vertex $1$ and Vertex $2$ contain one coin each.
- Aoki removes the coin from Vertex $2$. Now, Vertex $2$ contains one coin.
- Takahashi removes the coin from Vertex $2$. Now, there is no coin remaining on the tree.
- Aoki takes his turn when there is no coin on the tree and loses.
Input #2
6
1 2
2 3
2 4
4 6
5 6
Output #2
Second
Input #3
7
1 7
7 4
3 4
7 5
6 3
2 1
Output #3
First
题目信息
题面与样例版权归 AtCoder 及出题人所有;中文翻译由 AI 生成(CI 管线),如有出入请以原文为准。