import java.util.Scanner;

public class Main {

	public static void main(String[] args) {

		Scanner scan = new Scanner(System.in);

		int A = scan.nextInt();
		int B = scan.nextInt();
		int C = scan.nextInt();
		int D = scan.nextInt();

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


	}

	public static int atk(int atk, int hp) {

		hp -= atk;

		return hp;
	}

}


/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