#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <iomanip>
#include <cmath>
#include <stdio.h>
#include <queue>
#include <deque>
#include <cstdio>
#include <set>
#include <map>
#include <bitset>
#include <stack>
#include <cctype>
using namespace std;
int main() {
	long long l, r, m, k;
	cin >> l >> r >> m >> k;
	l *= k, r *= k;
	if ((l + m - 1) / m * m <= r) {
		cout << "Yes" << endl;
	}
	else {
		cout << "No" << endl;
	}
}