P23393 [AtCoder] Game on Tree
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题目描述

Problem Statement

There is a tree with N vertices numbered 1, 2, ..., N.
The edges of the tree are denoted by (x_i, y_i).
On this tree, Alice and Bob play a game against each other.
Starting from Alice, they alternately perform the following operation:

  • Select an existing edge and remove it from the tree, disconnecting it into two separate connected components. Then, remove the component that does not contain Vertex 1.

A player loses the game when he/she is unable to perform the operation.
Determine the winner of the game assuming that both players play optimally.

Input

Input is given from Standard Input in the following format:
N
x_1 y_1
x_2 y_2
:
x_{N-1} y_{N-1}

Output

Print Alice if Alice wins; print Bob if Bob wins.

Constraints

  • $2 \leq N \leq 100000$
  • $1 \leq x_i, y_i \leq N$
  • The given graph is a tree.

Sample Input 1

5
1 2
2 3
2 4
4 5

Sample Output 1

Alice

If Alice first removes the edge connecting Vertices 1 and 2, the tree becomes a single vertex tree containing only Vertex 1.
Since there is no edge anymore, Bob cannot perform the operation and Alice wins.

Sample Input 2

5
1 2
2 3
1 4
4 5

Sample Output 2

Bob

Sample Input 3

6
1 2
2 4
5 1
6 3
3 2

Sample Output 3

Alice

Sample Input 4

7
1 2
3 7
4 6
2 3
2 4
1 5

Sample Output 4

Bob

输入格式

见题面 Input 部分

输出格式

见题面 Output 部分

样例输入
5 1 2 2 3 2 4 4 5
样例输出
Alice