import java.util.Scanner;

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

        if(Math.ceil(A/D)>=Math.ceil(C/B)){
            System.out.println("Yes");
        } else{
            System.out.println("No");
        }

        sc.close();
    }
}
/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