Super long sums

Here's the problem statement: Super long sums
Accepted in the 7th try, after getting 6 Time Limit Exceeded errors. Moral of the story: don't use cin or cout as far as possible. Stick to ANSI C standards and use good ol' scanf and printf, though cumbersome!

#include "iostream"
#include "cstdio"

using namespace std;

main()
{
       int a[1000000];
       int n, i, j, x, y, m;

       cin>>n;

       for(i=0; i 0) printf("\n");
               scanf("%d", &m);
               for(j=0; j<m; j++) {
                       scanf("%d%d",&x,&y);
                       a[j] = x+y;
               }
               for(j--; j>=0; j--) {
                       if(a[j] > 9) {
                               a[j-1]++;
                               a[j] -= 10;
                       }
               }
               for(j=0; j<m; j++) printf("%d", a[j]);
               printf("\n");
       }

       return 0;
}