#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); ++i)
int main() {
    // Input
    long long H, W, N, K;
    cin >> H >> W >> N >> K;

    // Output
    if (H * W % N + (H * W % N == 0 ? N : 0) == K) cout << "YES" << endl;
    else cout << "NO" << endl;
}