1 #include <cstdio>
 2 
 3 const int MAXN = 1000;
 4 int f[MAXN+10];
 5 int n, m;
 6 int a, b;
 7 
 8 int find(int x)
 9 {
10     return x == f[x] ? x : f[x] = find(f[x]);
11 }
12 
13 void merge(int a, int b)
14 {
15     int t1 = find(a);
16     int t2 = find(b);
17     if(t1 != t2)
18         f[t1] = t2;
19 }
20 
21 int main()
22 {
23     while(scanf("%d%d", &n, &m), n){
24         for(int i = 1; i <= n; ++i)
25             f[i] = i;
26         while(m--){
27             scanf("%d%d", &a, &b);
28             merge(a, b);
29         }
30         int ans = 0;
31         for(int i = 1; i <= n; ++i){
32             if(f[i] == i)
33                 ++ans;
34         }
35         printf("%d\n", --ans);
36     }
37     return 0;
38 }