Light OJ Solution 1294 - Positive Negative Sign

Solve in C:

#include <bits/stdc++.h>
using namespace std;
int main()
{

    long long int i,a,r,n,m;
    scanf("%d",&a);
    for(i=1;i<=a;i++)
    {
        scanf("%lld%lld",&n,&m);
        r=(n*m)/2;
        printf("Case %lld: %lld\n",i,r);;
    }


}