Cliques Y16864

Given an undirected graph with $n$ vertices and $m$ edges, tell whether every connected component is a clique, that is, if all the vertices of the component are directly connected to each other.

Input

Input consists of several cases. Each case begins with $n$ and $m$, followed by $m$ pairs $x$ $y$, with $x \ne y$, indicating an edge between $x$ and $y$. Suppose $1 \le n \le 10^5$, $0 \le m \le 5n$, that the vertices are numbered between 0 and $n-1$, and that there are no repeated edges.

Output

For each given graph, print “SI” if every connected component is a clique, and “NO” otherwise.

Observation

Even if a green light is obtained, only solutions that perform a single graph traversal will receive the maximum score.