#include  <bits/stdc++.h>
using namespace std;
static int fast_io = []() { std::ios::sync_with_stdio(false); cin.tie(nullptr); return 0; }();
int main(){
  int aa,ah,ta,th;
  cin>>th>>ta;
  cin>>ah>>aa;
  bool turn=true;
  while(true){  
    if(turn){
      if(ah-ta<=0){
        cout<<"Yes"<<"\n";  
        break;
      }
      else{
        ah-=ta;
      }
    }
    else{
        if(th-aa<=0){
          cout<<"No"<<"\n";
          break;  
        }
        else{
          th-=aa;
        }
    }
    turn=!turn;
  }
  return 0;
}