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

using ll = long long;

int main()
{
  int a_health, a_attach, b_health, b_attach;
  cin >> a_health >> a_attach >> b_health >> b_attach;
  int i=1;
  while(true){
    if(b_health <= a_attach*i){
      cout << "Yes" << endl;
      return 0;
    }else if(a_health <= b_attach*i){
      cout << "No" << endl;
      return 0;
    }
    i++;
  }

}