#include<bits/stdc++.h>
using namespace std;
int par[100010],rank[100010];
void init(int n){
	for(int i = 1 ; i <= n ; i++){
		par[i] = i;
		rank[i] = 0;
	}
}
int find(int x){
	if(par[x] == x) return x;
	else return par[x] = find(par[x]);
}
void unite(int x,int y){
	x = find(x);
	y = find(y);
	if(x == y) return;
	if(rank[x] == rank[y]) rank[x]++;
	if(rank[x] < rank[y]) par[x] = y;
	else par[y] = x;
}
int main(){
	int n,m,x,y,ans = 0;
	while(cin>>n){
		if(n == 0) break;
		cin>>m;
		init(1010);
		for(int i = 1,x,y ; i <= m ; i++){
			cin>>x>>y;
			unite(x,y);
		}
		for(int i = 1 ; i <= n ; i++){
			if(find(i) == i) ans++; 
		}
		cout<<ans - 1;
	}
	return 0;
}