I use GNU C++ to solve this problem. I passed all test from #1 to #14. But, I am wrong at test #15
Input:
1000000000 1000000000 999999999
Output:
1

But my answer is 4.

I think 999999999 ^ 2 can't cover the area of Theater Square 1000000000 ^ 2. Thus, we should use 4 flagstones to cover area of Theaer Square, can't use only 1 flagstone.
Please help me!
Thanks all!

Here's my soucre code

#include <iostream>
using namespace std;

int main()
{
    float m, n, k;
    cin >> n >> m >> k;
    float horizontal = m / k;
    float vertical = n / k;
   
    int horizontalInt = (int) horizontal;
    int verticalInt = (int) vertical;
   
    if (horizontalInt < horizontal)
    {
        horizontalInt++;       
    }
    if (verticalInt < vertical)
    {
        verticalInt ++;
    }
   
    cout << horizontalInt * verticalInt;
 
    return 0;
}