题目描述
A Simple Task
Given a simple graph, output the number of simple cycles in it. A simple cycle is a cycle with no repeated vertices or edges.
输入
The first line of input contains two integers n and m (1 ≤ n ≤ 19, 0 ≤ m) – respectively the number of vertices and edges of the graph. Each of the subsequent m lines contains two integers a and b, (1 ≤ a, b ≤ n, a ≠ b) indicating that vertices a and b are connected by an undirected edge. There is no more than one edge connecting any pair of vertices.
输出
Output the number of cycles in the given graph.