import java.util.Scanner;

public class Main {
	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		long l = sc.nextInt();
		long r = sc.nextInt();
		int m = sc.nextInt();
		int k = sc.nextInt();
		sc.close();

		long lk = l * k;
		long rk = r * k;
		if (lk % m == 0 || rk % m == 0 || lk / m < rk / m) {
			System.out.println("Yes");
		} else {
			System.out.println("No");
		}
	}
}