e-olymp
Problems

Multiedges

Multiedges

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 (1n100) and number of edges m (1m10000). 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.

Time limit 1 second
Memory limit 128 MiB
Input example #1
3 4
1 2
2 3
1 3
2 1
Output example #1
NO
Input example #2
3 4
1 2
2 3
1 3
2 3
Output example #2
YES