Very easy

Execution time limit is 1 second

Runtime memory usage limit is 128 megabytes

The undirected graph is given. Find all its bridges.

The first line contains two positive integers n and m (n ≤ 20000, m ≤ 200000) - the number of vertices and edges in a graph respectively. Each of the next m lines contains the description of one edge. The edge number i is described with two positive integers `b[i]`

, `e[i]`

(1 ≤ `b[i]`

, `e[i]`

≤ n) - the numbers of the vertices it connects.

Print in the first line the number b of bridges in a given graph. Print on the next line b integers - the edge numbers that are bridges, in increasing order. The edges are numbered from one in the order they are given at the input.

Input #1

Answer #1