Is it cyclic?

Write a program that, given a directed graph, determines whether the graph has any cycle or not.

Input

Input consists of several cases. Every case begins with the number of vertices $n$ and the number of arcs $m$ of a graph $G$ . Follow $m$ pairs $u$ , $v$ , indicating that there is an arc $u \rightarrow v$ in $G$ , with $u \neq v$ . Assume $1 \leq n \leq 10^{4}$ , $0 \leq m \leq 5n$ , and that for every pair of vertices $u$ and $v$ there is at most one arc of the kind $u \rightarrow v$ . Vertices are numbered from $0$ to $n-1$ .

Output

For every case, print “yes” or “no” depending on whether the graph has any cycle or not.

Problem information

Author: Unknown
Translator: Enric Rodríguez

Generation: 2026-01-25T11:17:49.335Z