hello. can you help me.what is the test 4. where can i find it.

#include <stdio.h>

int a[1000000],b[1000000] ,c[1000000];
void main()
{
 int n,i,cr=0;
 scanf("%d",&n);

 for(i=0;i<n;i++)
 {
  scanf("%d %d",&a[i],&b[i]);
 }
 for(i=n-1;i>=0;i--)
 {
  c[i  ]= (a[i]+b[i])%10+cr;
  cr= (a[i]+b[i]+cr)/10;
 }
 for(i=0;i<n;i++)
 {
  printf("%d",c[i]);
 }
}