import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int takahashiA = sc.nextInt();
        int takahashiKougeki = sc.nextInt();
        int aokiC = sc.nextInt();
        int aokiKougeki = sc.nextInt();

        while (takahashiA > 0 && aokiC > 0) {
            aokiC -= takahashiKougeki;
            if (aokiC <= 0) {
                System.out.println("Yes");
                break;
            }
            takahashiA -= aokiKougeki;
            if (takahashiA <= 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