import java.util.*; public class Main { public static void main (String[] args) { Scanner sc = new Scanner(System.in); int left = sc.nextInt(); int right = sc.nextInt(); int m = sc.nextInt(); long k = sc.nextInt(); long leftCount = (left * k - 1) / m; long rightCount = right * k / m; if (leftCount == rightCount) { System.out.println("No"); } else { System.out.println("Yes"); } } }