https://vjudge.net/problem/POJ-1611
#include<iostream>
#include<algorithm>
using namespace std;
const int N=50010;
int n,m;
int p[N];
int find(int x)
{
if(p[x]!=x) p[x]=find(p[x]);
return p[x];
}
int main()
{
ios::sync_with_stdio(false);
cin.tie(0); cout.tie(0);
int cnt=1;
while(cin>>n>>m)
{
if(n==0 || m==0)
break;
for(int i=1;i<=n;i++) p[i]=i;
int a,b,t1,t2;
while(m--)
{
cin>>a>>b;
t1=find(a),t2=find(b);
if(t1!=t2)
p[t1]=t2;
}
int ans=0;
for(int i=1;i<=n;i++)
if(p[i]==i)
ans++;
cout<<"Case "<<cnt++<<": "<<ans<<"\n";
}
return 0;
}