Hackerrank Ad Infinitum - Math Programming Contest June'14 - Easy Sum solution

Hackerrank  Ad Infinitum - Math Programming Contest June'14 - Easy Sum: https://www.hackerrank.com/contests/infinitum-jun14/challenges/easy-sum

Hackerrank  Ad Infinitum - Math Programming Contest June'14 - Easy Sum editorial: https://www.hackerrank.com/contests/infinitum-jun14/challenges/easy-sum/editorial

Hackerrank  Ad Infinitum - Math Programming Contest June'14 - Easy Sum solution:

#include <iostream>
#include <cstdio>
using namespace std;

int main()
{
   long long int t, n, m, s, c;
   scanf("%lld", &t);
   while(t--) {
       scanf("%lld%lld", &n, &m);
       s=c=0;
       s=m*(m-1)/2;
       c=s*(n/m);
       s=n%m;
       c+=s*(s+1)/2;
       printf("%lld\n", c);
    }
   return 0;
}

note: use long long int. i used int and got 10 pts during the contest, after contest i changed it to long long int and got AC with 20 pts :(