1 #include<stdio.h>
 2 #include<stdlib.h>
 3 #include<math.h>
 4 
 5 int bin[1005];
 6 
 7 int find(int r){
 8     while(r != bin[r]){
 9         r = bin[r];
10     }
11     return r;
12 }
13 
14 int memge(int x, int y){
15     x = find(x);
16     y = find(y);
17     if(x != y){
18         bin[x] = y;
19     }
20     return 0;
21 }
22 
23 int main(){
24     int n, m, i, x, y, cout;
25     while(scanf("%d", &n) && n){
26         scanf("%d", &m);
27         for(i = 1; i <= n; i ++){
28             bin[i] = i;
29         }
30         for(i = 0; i < m; i ++){
31             scanf("%d %d", &x, &y);
32             memge(x, y);
33         }
34         cout = -1;
35         for(i = 1; i <= n; i ++){
36             if(i == bin[i]){
37                 cout ++;
38             }
39         }
40         printf("%d\n", cout);
41     }
42     return 0;
43 }