import java.util.*;

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

        System.out.println(l <= m && m <= r * k || k == 0 ? "Yes" : "No");
    }
}