How Many Points of Intersection?

http://acm.hust.edu.cn/vjudge/contest/view.action?cid=29592#problem/K

// File Name: bo_jwolf11.cpp// Author: rudolf// Created Time: 2013年08月19日 星期一 21:25:25#include<vector>#include<list>#include<map>#include<set>#include<deque>#include<stack>#include<bitset>#include<algorithm>#include<functional>#include<numeric>#include<utility>#include<sstream>#include<iostream>#include<iomanip>#include<cstdio>#include<cmath>#include<cstdlib>#include<cstring>#include<ctime>using namespace std;int main(){long long n , m , Case = 0 , ans ;while( cin >> n >> m && ( n + m ) ){Case++ ;ans = n * ( n - 1 ) / 2 * m * ( m - 1 ) / 2  ;printf( "Case %lld: %lld\n" , Case , ans ) ;}return 0;}