1 # include <stdio.h>
 2 # include <string.h>
 3 int pre[1005],t[1005];
 4 int find(int x)
 5 {
 6     int r = x;
 7     while (pre[r] != r)
 8         r = pre[r];
 9     int i= x,j;
10     while(i != r)
11     {
12         j = pre[i];
13         pre[i] = r;
14         i = j;
15     }
16     return r;
17 }
18 void Union(int i,int j)
19 {
20     int x = find(i);
21     int y = find(j);
22     if (x != y)
23         pre[x] = y;
24 }
25 
26 int main ()
27 {
28     int n,m,i;
29     while (scanf("%d",&n) != EOF&&n)
30     {
31         for (i = 1; i <= n; i ++)
32         pre[i] = i;
33         scanf("%d",&m);
34         int a,b;
35         for (i = 1; i <= m; i ++)
36         {
37             scanf("%d%d",&a,&b);
38             Union(a,b);    
39         } 
40         int sum = 0;
41         memset(t,0,sizeof(t));
42         for (i = 1; i <= n; i ++)
43             t[find(i)] = 1;
44         for (i = 1; i <= n; i ++)
45             if (t[i])
46                 sum ++;
47         printf("%d\n",sum-1);    
48     }
49     return 0;
50 }