import java.util.*;
class Main{
 static public void main(String args[]){
  Scanner sc=new Scanner(System.in); 
   boolean flag;
   int a,b,c,d;
   a=sc.nextInt();
   b=sc.nextInt();//kougeki
   c=sc.nextInt();
   d=sc.nextInt();//kougeki
   
   while(true){
  	
     c-=b;
	 
	 	if(c<=0){
	 	flag=true;break;
		}

	 a-=d;
	    if(a<=0){
	 	flag=false;break;
		}
		
	 else continue;
   }
   
   if(flag)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