4 2
1 3
4 3
3 3
1 2
1 3
2 3
5 2
1 2
3 5
999 0
0

1
0
2
998

Hint
Hint
 
Huge input, scanf is recommended.

#include<cstdio>
#include<iostream>
using namespace std;
int father[1001];
void init()
{
    for(int i=1;i<=1001;i++)
        father[i]=i;
}
int Find(int x)
{
    return x==father[x]?x:father[x]=Find(father[x]);
}
void Union(int x,int y)
{
    int x1=Find(x);
    int y1=Find(y);
    if(x1!=y1)
        father[y1]=x1;
}
int main()
{
    int n,m;
    while(scanf("%d",&n)!=EOF)
    {
        if(!n)
            return 0;
        cin>>m;
        int c=0;
        init();
        int a,b;
        while(m--)
        {
            cin>>a>>b;
            Union(a,b);
        }
        for(int i=1;i<=n;i++)
        if(father[i]==i)
            c++;
        cout<<c-1<<endl;
    }
    return 0;
}