UVA - 10489 - Boxes of Chocolates

#include<stdio.h>

int main()
{

   long n,friends,boxes,k,product,sum,temp;
   scanf("%ld",&n);
   while(n--){
      scanf("%ld %ld",&friends,&boxes);
      sum=0;
      while(boxes--){
         product=1;
         scanf("%ld",&k);
         while(k--){
            scanf("%ld",&temp);
            product=(product*temp)%friends;
         }
         sum=(sum+product)%friends;
      }
      printf("%ld\n",sum);
   }
   return 0;
}