1 #include <iostream>
 2 #include <cstdio>
 3 
 4  #define MAX 1000
 5 
 6 using namespace std;
 7 
 8 int parent[MAX];
 9 int N;
10 
11 void init()
12 {
13     for (int i = 0; i < N; i++) parent[i] = i;
14 }
15 
16 int find(int x)
17 {
18     int i = x, r = x;
19     while (r != parent[r]) r = parent[r];
20     int j;
21     while (i != r)
22     {
23         j = parent[i];
24         parent[i] = r;
25         i = j;
26     }
27     return r;
28 }
29 
30 void merge(int x, int y)
31 {
32     x = find(x);
33     y = find(y);
34     if (x != y) parent[x] = y;
35 }
36 
37 int main()
38 {
39     //freopen("in.txt", "r", stdin);
40     int m;
41     while (scanf("%d", &N), N != 0)
42     {
43         scanf("%d", &m);
44         int res = 0;
45         init();
46         while (m--)
47         {
48             int x, y;
49             scanf("%d %d", &x, &y);
50             merge(x, y);
51         }
52         for (int i = 0; i < N; i++)
53         {
54             if (i == parent[i]) res++;
55         }
56         printf("%d\n", res - 1);
57     }
58 }
59