#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define SZ(v) ((int)(v.size()))
#define pb push_back
void run () {
    ll W, H, w, h;
    cin >> W >> H >> w >> h;
    ll a = ((W / w + 1) / 2);
    ll b = ((H / h + 1) / 2);
    cout << a * b << '\n';
}
int main () {
//  freopen("run.in", "r", stdin);
    freopen("garage.in", "rt", stdin);
    freopen("garage.out", "wt", stdout);
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    int tt = 1;
//  cin >> tt;
    while (tt--)
        run();
    return 0;
}