import java.util.Scanner;

public class Main {

	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);

		int hpa = sc.nextInt(), ata = sc.nextInt(), hpb = sc.nextInt(), atb = sc.nextInt();

		while(true) {
			hpb -= ata;
			if(hpb <= 0) {
				System.out.println("Yes");
				break;
			}
			hpa -= atb;
			if(hpa <= 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