1 #include<stdio.h>
 2 int p[1001];
 3 int find(int x)
 4 {
 5     if(x!=p[x])p[x]=find(p[x]);
 6     return p[x];
 7 }
 8 int hebing(int x,int y)
 9 {
10     p[x]=y;
11     return 1;
12 }
13 int main()
14 {
15     int a,b,c,d,i,n,x,y,sum=0;
16         while(scanf("%d",&a)!=EOF)
17         {
18             if(a==0)break;
19             scanf("%d",&b);
20             if(b==0){printf("%d\n",a-1);}
21             else{
22             sum=0;
23             for(i=1;i<=a;i++)
24             {
25                 p[i]=i;
26             }
27             for(i=0;i<b;i++)
28             {
29                 scanf("%d%d",&x,&y);
30                 x=find(x);
31                 y=find(y);
32                 hebing(x,y);
33             }
34             for(i=1;i<=a;i++)
35             {
36                 if(p[i]==i)sum++;
37             }
38             printf("%d",sum-1);
39            printf("\n");
40         }
41         }
42     return 0;
43 }