Inevitability#1942
Vasya lives at the first vertex of a connected undirected graph with vertices and edges. Each day, he walks to school, which is located at vertex number . Vasya tries to take a different route to school every day, but he noticed that there are some edges that he must cross every day, regardless of which route he takes. Help Vasya find all such edges.
The first line of the input contains two natural numbers and — the number of vertices and edges in the graph, respectively (n \leq 20000, m \leq 200000).
The following lines describe the edges, one per line. Edge is described by two natural numbers b_i and e_i — the endpoints of the edge (1 \leq b_i, e_i \leq n).
The first line of the output should contain a single natural number — the number of edges that Vasya must traverse on any path to school. The second line should list these edge numbers in ascending order. The edges are numbered starting from one, according to their order in the input.
Example 1