I was solving this problem Counting Inversions Revisited Problem Code: INVYCNT. Here it is clearly mentioned that

n <= 100 and a[i] <= 10^ 9

I tried to solve this problem using int array but I got WA.

WA code link

When I changed the array type to long long I got AC

AC code link

Why is this happening? int type array can store array elements of size 10^9, then why is this happening? Can anyone give some insight into this?