#include <bits/stdc++.h>
 
using namespace std;
 

 
int main()
{
    
    int a,b,c,d;
    cin>>a>>b>>c>>d;
    int cnt=1;
    while(a>0 && c>0)
    {
        if(cnt%2!=0)
           c=c-b;
           
        else
          a=a-d;
          
          cnt++;
    }
    
    if(a<=0)
      printf("No");
      
    else
       printf("Yes");
       
       
    
    
    
     return 0;   
         
  
  
}