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 <stdio.h>
int b[10001];
int findx(int x)
{
    int r;
    r=x;
    while(r!=b[r])
        r=b[r];
    return r;
}
void merge(int x,int y)
{
    int fx,fy;
    fx=findx(x);
    fy=findx(y);
    if(fx!=fy)
        b[fx]=fy;
}
int main()
{
    int x,m,n,y,i,j;
    while(scanf("%d %d",&n,&m)!=EOF)
    {
        if(n==0) break;
        for(i=1;i<=n;i++)
        {
            b[i]=i;
        }
        while(m--)
        {
            scanf("%d %d",&x,&y);
            merge(x,y);
        }
        j=-1;
        for(i=1;i<=n;i++)
        {
            if(b[i]==i) j++;
        }
        printf("%d\n",j);
    }
    return 0;
}