UVa：10790 - How Many Points of Intersection?

#include<stdio.h>
int main(){
    long long sum;
    int a, b;
    int t = 1;
    while(scanf("%d%d", &a, &b) != EOF){
        if(!a && !b)
            break;
        printf("Case %d: %lld\n", t++, (long long)a * (a - 1) * b * (b - 1) / 4);
    }
    return 0;
}