Uva 10790 - How Many Points of Intersection?

水题一只

上面取2个点,下面取两个点就一定有一个交点

Cn2即好

试验了一下

Uva接受lld

不认I64d

#include<stdio.h>#define LL long longLL C2(LL x){return x*(x-1)/2;}int main(){LL a,b;int t=0;while(scanf("%lld%lld",&a,&b)!=EOF){if(a==0&&b==0)break;printf("Case %d: ",++t);printf("%lld\n",C2(a)*C2(b));}return 0;}