import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int A = Integer.parseInt(sc.next());
		int B = Integer.parseInt(sc.next());
		int C = Integer.parseInt(sc.next());
		int D = Integer.parseInt(sc.next());
		sc.close();

		while (true) {
			C -= B;
			if (C <= 0) {
				System.out.println("Yes");
				break;
			}
			A -= D;
			if (A <= 0) {
				System.out.println("No");
				break;
			}
		}

	}

}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz