import java.util.Scanner;
public class Main {
 public static void main(String[]args){
Scanner scan = new Scanner(System.in);
  int A = scan.nextInt();
  int B = scan.nextInt();
  int C = scan.nextInt(); 
  int D = scan.nextInt();
  while ((A>0) && (C>0)){
   C=C-B;
   if (C<=0){
    System.out.println("Yes");}
   A=A-D;
   if ((A<=0) && (C>0)){
    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