import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner s = new Scanner(System.in);
        String[] in = s.nextLine().split(" ");
        int A = Integer.parseInt(in[0]);
        int B = Integer.parseInt(in[1]);
        int C = Integer.parseInt(in[2]);
        int D = Integer.parseInt(in[3]);

        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