黑暗爆炸OJ

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#2350. [Baltic2011]Tree Mirroring

Statistics 下载数据

Description

Input

Output

Sample Input

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

Sample Output

NO

Hint

Source

[BZOJ 2350] [Poi2011] Party 【Special】