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

int main() {
  int HPt, ATKt, HPa, ATKa;
  cin >> HPt >> ATKt >> HPa >> ATKa;
  for(int i; ; i++){
    HPa-=ATKt;
    if(HPa==ATKt<0) {
      cout << "Yes" << endl;
      break;
    }
    HPt-=ATKa;
    if(HPt==ATKa<0) {
      cout << "No" << endl;
      break;
    }
  }
}