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

int main()
{
	long long H, W, N, K;
	cin >> H >> W >> N >> K;

	long long a = H * W;
	string ans = "NO";
	if( N >= a ) {
		if( a == K ) ans = "YES";
	}
	else {
		long long m = a % N;
		if( m == 0 ) m = N;
		if( m == K ) ans = "YES";
	}

	cout << ans << endl;
}