

import java.util.Scanner;

public class Main{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		int thp = sc.nextInt();
		int ta = sc.nextInt();
		int ahp = sc.nextInt();
		int aa = sc.nextInt();

		while (thp > 0) {
			ahp -= ta;
			if (ahp <= 0)
				break;
			thp -= aa;
		}
		if (thp <= 0)
			System.out.println("No");
		else
			System.out.println("Yes");
	}

}

/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