#include <iostream>
#include  <cstdio>
using namespace std;
int fa[1005];

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


int main() {
    int n,m;
    while(cin >> n >> m){
        if(n == 0){
            break;
        }

        for(int i = 1;i <= n;i++){
            fa[i] = i;
        }
        for(int i = 1;i <= m;i++){
            int j,k;
            cin >> j >> k;
            fa[find(k)] = find(j);
        }
        int sum = 0;
        for(int i = 1;i <= n;i++){
            if(fa[i] == i){
                sum++;
            }
        }
        cout << sum - 1 << endl;

    }
}