import java.util.*;

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

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