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

int main() {
  int tHp,tAtk,aHp,aAtk;
  string kekka;
  cin >> tHp >> tAtk >> aHp >> aAtk;
  
  while(true){
    tHp -= aAtk;
    aHp -= tAtk;
    
    if(aHp <= 0){
      cout << "Yes";
      break;
    }
    
    if(tHp <= 0){
      cout << "No";
      break;
    }
  }
}
