#include <iostream>
#include <vector>
#include <cstring>
#include <string>
#include <algorithm>
#include <iomanip>
using namespace std;
typedef long long ll;

int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);

	ll H, W, N, K;
	cin >> H >> W >> N >> K;

	H += W - 1;
	if(H % N == K) {
		cout << "YES" << endl;
	}
	else {
		cout << "NO" << endl;
	}
}