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 ≤ n ≤ 10⁴, 0 ≤ m ≤ 5n, that vertices are numbered from 0 to n − 1, x ≠ 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.