#include<cstdio>
using namespace std;
int father[1001];
int pc=0;
int find(int a)
{
if(father[a]!=a) father[a]=find(father[a]);
return father[a];
}
int main()
{
char ch;
int n,m;
begin:;
scanf("%d%d",&n,&m);
if(n==0)return 0;
for(int i=1;i<=n;i++)
{
father[i]=i;
}
for(int i=0,a,b,fa,fb;i<m;i++)
{
scanf("%d%d",&a,&b);
fa=find(a);
fb=find(b);
if (fa!=fb) father[fa]=fb;
}
for(int i=1;i<=n;i++)
{
if(father[i]==i) pc++;
}
if(m==0)printf("%d\n",n-1);
else if(pc<=1)printf("%d\n",0);
else printf("%d\n",pc-1);
goto begin;
}