#include<iostream>#include<cstring>#include<cstdio>using namespace std;int pre[1005],t[1005],n,m,a,b;int findd(int x){    int root = x;    while(pre[root] != root)    root = pre[root];    int i = x,j;    while(pre[i] != root)    {        j = pre[i];        pre[i] = root;        i = j;    }    return root;}void join(int a,int b){    int x = findd(a),y = findd(b);    if(x != y)  pre[x] = y;}int main(){    while(scanf("%d",&n) && n)    {        scanf("%d",&m);        for(int i = 1;i <= n;i++)   pre[i] = i;        while(m--)        {            scanf("%d%d",&a,&b);            join(a,b);        }        memset(t,0,sizeof(t));        for(int i = 1;i <= n;i++)        {            t[findd(i)] = 1;        }        int ans = 0;        for(int i = 1;i <= n;i++)        {            if(t[i])    ans++;        }        printf("%d\n",ans-1);    }    return 0;}