import java.util.*;

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int takahashi_hp = sc.nextInt();
        int takahashi_att = sc.nextInt();
        int aoki_hp = sc.nextInt();
        int aoki_att = sc.nextInt();
        while (true) {
            aoki_hp -= takahashi_att;
            if (aoki_hp <= 0) {
                System.out.println("Yes");
                break;
            }
            takahashi_hp -= aoki_att;
            if (takahashi_hp <= 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