import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        Integer A = input.nextInt();
        Integer B = input.nextInt();
        Integer C = input.nextInt();
        Integer D = input.nextInt();

        Integer ConfirmTimeT = (int)Math.ceil((float)C / B);
        Integer ConfirmTimeA = (int)Math.ceil((float)A / D);

        if (ConfirmTimeT <= ConfirmTimeA) System.out.println("Yes");
        else System.out.println("No");
    }
}

/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