UVa 369 Combinations

#include<bits/stdc++.h>
#define ll long long

using namespace std;

ll combi(ll n,ll m)
{
 ll r,i;
 r=1;
 if(n-m<m) m=n-m;
 
 for(i=1; i<m+1; i++,n--)
 {
  r=r*n;
  r=r/i;
 }
 
 return r;
}

int main()
{
 ll m,n;
 ll c;
 
 while(cin>>n>>m)
 {
  if(n==0 && m==0) break;
  c=combi(n,m);
  cout<<n<<" things taken "<<m<<" at a time is "<<c<<" exactly."<<endl;
 }
 
 return 0;
}