//新生训练

#include <iostream>
#include <algorithm>
#include <bits/stdc++.h>
using namespace std;

#define N 1010

int fa[N];

int Find(int x)
{

    if (x != fa[x])
    {

        fa[x] = Find(fa[x]);
    }
    return fa[x];
}

void Union(int x, int y)
{

    int a = Find(x);
    int b = Find(y);

    if (a != b)
    {
        fa[a] = b;
    }
}

int main()
{

    while (1)
    {

        int n, m, i, ans = 0, x, y;
        scanf("%d", &n);
        if (n == 0)
        {

            break;
        }
        scanf("%d", &m);
        for (int i = 1; i <= n; i++)
        {

            fa[i] = i;
        }
        for (int i = 0; i < m; i++)
        {

            scanf("%d%d", &x, &y);
            Union(x, y);
        }
        for (int i = 1; i <= n; i++)
        {

            if (i == fa[i])
            {

                ans++;
            }
        }
        printf("%d\n", ans - 1);
    }
    return 0;
}

 //学习了新内容，开始接触图论基础了；

~~~//仅当笔者个人备忘录使用。