Competitions

# Graph representation

# 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** (**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.

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