#include
    
     int father[1005],depth[1005];void init(){    int i;    for(i = 1; i < 1005;i ++)    {        father[i] = i;        depth[i] = 0;    }}int find(int x){    if(x==father[x])        return x;    else        return father[x] = find(father[x]); 　　//优化树的高度；}void unit(int x,int y){    x = find(x);    y = find(y);    if(x==y)        return ;    if(depth[x]
     
      depth[y])            father[y] = father[x];        else        {            father[x] = father[y];            depth[y]++;        }    }}int main(){    int n,m,a,b,j,gr;    while(~scanf("%d%d",&n,&m)&&n!=0)    {        gr = 0;        init();        while(m--)        {            scanf("%d%d",&a,&b);            unit(a,b);        }        for(j = 1;j <= n;j ++)        {            if(j==father[j])                gr++;        }        printf("%d\n",gr-1);    }    return 0;}