A directed graph is given with a list of edges. Check whether it contains multiedges.

Input

The first line contains number of vertices in a graph n (1 ≤ n ≤ 100) and number of edges m (1 ≤ m ≤ 10000). Each of the next m lines contains pair of integers - the edges of the graph.

Output

Print YES if graph contains multiedges and NO otherwise.