Virus

Interview

Time limit1sMemory limit128 MB

Summary

Count how many computers other than computer 1 lie in computer 1's connected component of a small undirected graph.

Level: Easy2 of 10
Topics: Graph, BFS, DFS
Solved: No attempts yet

Problem

A worm virus spreads along network connections. If one computer is infected, every computer in the same connected component can become infected.

Computer 1 is infected. Given the number of computers and the pairs of computers directly connected by the network, determine how many other computers become infected through computer 1.

Do not count computer 1 itself.

Input

The first line contains the number of computers N. N is a positive integer no greater than 100, and the computers are numbered from 1 to N.

The second line contains the number M of pairs of computers that are directly connected in the network. Each of the next M lines contains two computer numbers a and b that are directly connected.

Output

Print one integer: the number of computers other than computer 1 that become infected through computer 1.

Examples1

Example 1
Input
```
7
6
1 2
2 3
1 5
5 2
5 6
4 7
```
Expected output
```
4
```