#include<cstdio>
using namespace std;
#define N 1010
int fa[N];

int Find(int x)
{
    if(x!=fa[x])
        fa[x]=Find(fa[x]);
    return fa[x];
}

void Union(int x,int y)
{
    int a=Find(x);
    int b=Find(y);
    if(a!=b)
        fa[a]=b;
}

int main()
{
    while(1)
    {
        int n,m,i,ans=0,x,y;
        scanf("%d",&n);
        if(n==0)
            break;
        scanf("%d",&m);
        for(i=1;i<=n;i++)
            fa[i]=i;
        for(i=0;i<m;i++)
        {
            scanf("%d%d",&x,&y);
            Union(x,y);
        }
        for(i=1;i<=n;i++)
        {
            if(i==fa[i])
                ans++;
        }
        printf("%d\n",ans-1);
    }
    return 0;
}