#include <iostream>
using namespace std;
int main()
{
    int n,m,a,b,k=0,n1,m1;
    cin >> n >> m >> a >> b;
    k= (n / a) * (m / b);
    n1= n%a;m1 = m% b; n-=n1;
    if (n1>0)
    {
        if (( m/b) *b == m) k+=(m/b); else k+=(m/b)+1;
    }
    if (m1>0) k+=(n/a);
    cout << k;
}