Squares in a graph

You are given an undirected graph $G$ . Let us define a square as any cycle of length exactly four in $G$ . Can you count the number of squares in $G$ ?

Input

Input consists of several cases. Every case begins with two natural numbers $n$ and $m$ , which are respectively the number of vertices and the number of edges of $G$ . Follow $m$ pairs $x$ $y$ to indicate that there is an edge connecting vertices $x$ and $y$ . Assume $0 \le n \le 2000$ and $0 \le m \le 10n$ . Vertices are numbered starting at 0. There are no edges of the kind $x$ $x$ , nor repeated edges.

Output

For every given $G$ , print its number of squares.

Problem information

Author: Salvador Roura

Generation: 2026-01-25T12:23:07.685Z