The input contains several test cases, ended by a line of “-1 -1”.
Each test case begins with a line of two integers n ( 1 <= n <= 10) and m (0 <= m <= 30), indicating the number of vertexes and edges in the graph. All vertexes are numbered from 0 to n-1.
Then m lines follow. Each line contains two integers p and q ( 0 <= p, q < n) , indicating there is an edge between vertex p and vertex q.
It is possible that the graph contains more than one edge between two vertexes and self-loops.