#include<stdio.h>

int p[1000];

int Find(int i)
{
	return i==p[i]?i:p[i]=Find(p[i]);
}

void Union(int a,int b)
{
	p[a]=b;
}

int main()
{
	int n,m,i,s,e,a,b,ans;
	while(scanf("%d",&n)!=EOF,n)
	{
		scanf("%d",&m);
		for(i=1;i<=n;i++)
			p[i]=i;
		while(m--)
		{
			scanf("%d%d",&s,&e);
			a=Find(s);
			b=Find(e);
			if(a!=b)
				p[a]=b;
		}
		for(ans=0,i=1;i<=n;i++)
			if(p[i]==i)
				ans++;
		printf("%d\n",ans-1);
	}
	return 0;
}
/**************************************************************
	Problem: 2203
	User: admin
	Language: C++
	Result: Accepted
	Time:9 ms
	Memory:1148 kb
****************************************************************/