#include <iostream>
#include <vector>
#include<map>
#include<string>
#include<algorithm>
#include<sstream>
#include<cmath>
using namespace std;


int main() {
	long long int l,r,m,k;
	cin >> l>>r>>m>>k;
	int n=0;
	int count=0;
	bool flag = false;
	if (l * k <= m && r * k >= m) {
		flag = true;
	}
	if (flag) {
		cout << "Yes";
	}
	else {
		cout << "No";
	}

}