A junior admin suspects a faulty configuration created a routing loop — Rakib must check if the network contains any cycle at all. Given an undirected graph with N nodes and M edges, print "YES" if it contains a cycle, else "NO".
Input
Line1: N M. Next M lines: u v.
Output
"YES" or "NO".
Constraints
1 ≤ N ≤ 10^5, 0 ≤ M ≤ 2×10^5
Sample Input
4 4 1 2 2 3 3 4 4 1
Sample Output
YES
main.c
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