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

int main()
{
	long long L, R, M, K;
	cin >> L >> R >> M >> K;

	string ans = "YES";
	if( K == 0 ) {
	}
	else {
		long long l = L * K;
		long long r = R * K;
		long long m = M;
		while( m < l ) m += K;
		if( m > r ) ans = "NO";
	}

	cout << ans << endl;
}