import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Scanner;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 *
 * @author silviase
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        No1048ZeroAdvanced solver = new No1048ZeroAdvanced();
        solver.solve(1, in, out);
        out.close();
    }

    static class No1048ZeroAdvanced {
        public void solve(int testNumber, Scanner in, PrintWriter out) {

            long l = in.nextLong();
            long r = in.nextLong();
            long m = in.nextLong();
            long k = in.nextLong();

            out.println(k == 0 ? "Yes" : (k * r) / m > (k * l - 1) / m ? "Yes" : "No");

        }

    }
}