import java.io.*;
import java.util.*;
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();
    while(a>=0 || c>=0)
    {
      c-=b;
      if(c<=0)
       {
         System.out.println("Yes");
         break;
       } 
      a-=d;
      if(a<=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