老规矩，抄一波QSC，自己的写在后面   E. Bear and Forgotten Tree 2 题目连接： http://www.codeforces.com/contest/653/problem/E Description A tree is a connected undirected graph consisting of n vertices and n  -  1 edges.

Bear and Up-Down time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output The life goes up and down, just like nice sequences. S