#include <bits/stdc++.h>

#define REP(i,l,u) for(int (i)=(int)(l);(i)<(int)(u);++(i))

using namespace std;

typedef int64_t ll;

const int INF = 1e8;
const double EPS = 1e-10;

int main() {
    ios_base::sync_with_stdio(false);
    ll H, W, N, K;
    cin >> H >> W >> N >> K;
    cout << ((H+W-1)%N==K ? "YES" : "NO") << endl;
}