## Problem C. Biconnectivity ≡

• problems
 Author: StdAlg Time limit: 1 sec Input file: input.txt Memory limit: 64 Mb Output file: output.txt

### Statement

You are to write a program that receives a connected undirected graph and finds all its articulation points, which are the vertices that, if removed, leave disconnected graph.

### Input file format

Input file contains two integers N and M. Vertices are numbered with integer numbers from 1 to N. M is the number of edges. Each of next M lines contain pair of integers — numbers of vertices connected by an edge. There are no pairs of equal numbers.

### Output file format

Output file must contain integer representing a quantity of articulation points, followed by numbers of corresponding vertices in arbitrary order.

### Constraints

1 ≤ N, M ≤ 100000

### Sample tests

No. Input file (input.txt) Output file (output.txt)
1
5 6
1 2
1 3
2 3
1 4
1 5
4 5
1 1

0.068s 0.016s 13