Two colors P29033

Write a program that, given an undirected graph, tells if we can paint all vertices with only two colors, in such a way that no two neighboring vertices have the same color.

Input

Input consists of several cases, each with the number of vertices $n$ and the number of edges $m$, followed by $m$ pairs $x$ $y$ indicating an edge between $x$ and $y$. Suppose $1 \le n \le 10^4$, $0 \le m \le 5n$, that vertices are numbered from 0 to $n - 1$, $x \ne y$, and that there is no more than one edge between any pair $x$ $y$.

Output

For every case, print “yes” if the graph is two-colorable, and “no” otherwise.