#include <bits/stdc++.h>
using namespace std;

void no_166(void) {
    long long h, w;
    cin >> h >> w;
    long long n, k;
    cin >> n >> k;
    long long total = (h * w) / n;
    long long remain = (h * w) % n;

    if (k == n) k = 0;

    if (remain == k)
        cout << "YES" << endl;
    else
        cout << "NO" << endl;
}

int main(void) {
    no_166();
    return 0;
}