import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int tHp = sc.nextInt();
        int tAtk = sc.nextInt();
        int aHP = sc.nextInt();
        int aAtk = sc.nextInt();
        boolean Tattack = true;

        while (tHp > 0 && aHP > 0) {
            if (Tattack) {
                aHP -= tAtk;
                Tattack = false;
            } else {
                tHp -= aAtk;
                Tattack = true;
            }
        }
        if (tHp > 0) {
            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