import java.util.*;
//import java.util.Arrays;

public class Main { //クラス名はMain
    public static void main(String[] args) {
      Scanner sc = new Scanner(System.in);
      int a = Integer.parseInt(sc.next());
      int b = Integer.parseInt(sc.next());
      int c = Integer.parseInt(sc.next());
      int d = Integer.parseInt(sc.next());

      double x = (double)a/d;
      double y = (double)c/b;
      x = Math.ceil(x);
      y = Math.ceil(y);

      if(x>=y){
        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