#include<stdio.h>
#include <vector>
#include <list>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <algorithm>
#include <sstream>
#include <iostream>
#include <string>
#include <stdio.h>

using namespace std;

int main() {

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

	int sum = W*H - K;

	if (sum > 0 && sum % N == 0) cout << "YES" << endl;
	else cout << "NO" << endl;

	return 0;
}