Negative cycle detection

Write a program that, given a directed graph with positive and/or negative costs at the arcs, detects if there is a negative cycle in the graph.

Input

Input consists of several cases. Every case begins with the number of vertices $n$ and the number of arcs $m$ . Follow $m$ triples $u, v, c$ , indicating that there is an arc $u \to v$ of cost $c$ , where $u \ne v$ , $-10^6 \le c \le 10^6$ . Assume $1 \le n \le 10^4$ , $0 \le m \le 5n$ , and that for every pair of vertices $u$ and $v$ there is at most one arc of the kind $u \to v$ . All numbers are integers. Vertices are numbered from 0 to $n-1$ .

Output

For every case, print "YES" if there is a negative cycle in the graph, and "NO" otherwise.

Problem information

Author: Jordi Petit

Generation: 2026-01-25T10:35:31.051Z