Petya is an unexperienced programming contestant. Recently he has come across the following problem: You are given a non-directed graph which consists of n nodes and m edges. Your task is to determine whether the graph contains a Hamiltonian path. Petya wrote a quick bug-free code which he believes solves this problem. After that Petya decided to give this problem for April Fools Day contest. Unfortunately, Petya might have made a mistake, and it's quite possible that his algorithm is wrong. But this isn't a good excuse to leave the contest without submitting this problem, is it?
输入描述:
The first line contains two integers n, m(1 ≤ n ≤ 20; 0 ≤ m ≤ 400). Next m lines contain pairs of integers vi, ui(1 ≤ vi, ui ≤ n).
输出描述:
Follow the format of Petya's code output.
示例1
输入
2 3<br />1 2<br />2 1<br />1 1<br />3 0<br />10 20<br />3 10<br />4 6<br />4 9<br />7 5<br />8 8<br />3 10<br />9 7<br />5 2<br />9 2<br />10 6<br />10 4<br />1 1<br />7 2<br />8 4<br />7 2<br />1 8<br />5 4<br />10 2<br />8 5<br />5 2<br />
输出
Yes<br />No<br />No<br />
加载中...