import java.util.Scanner;

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();

		int count = 0;

		while (true) {
			if ((count % 2) == 0) {
				C -= B;
				if (C <= 0) {
					System.out.println("Yes");
					break;
				}
			} else {
				A -= D;
				if (A <= 0) {
					System.out.println("No");
					break;
				}
			}
			count++;
		}
	}
}
/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