import java.util.Scanner;
public class Main
{
    public static void main(String [] args)
    {
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt(); int b = sc.nextInt(); int c = sc.nextInt(); int d = sc.nextInt(); boolean ans = false;
        for (int i = 0; i <= 100; i++) {
            if (a - d * i > 0 && c - b * (i + 1) <= 0) ans = true;
        }
        System.out.println(ans ? "Yes" : "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