#include<bits/stdc++.h>
using namespace std;
int main() {
  int a,b,c,d,ans,turn = 0;
  cin >> a >> b >> c >> d;
  while((c>0) && (a>0)) {
    if(turn % 2 == 0) c -= b;
    if(turn % 2 == 1) a -= d;
      ++turn;
    }
  if(turn % 2 == 1) cout << "Yes" << endl;
  else cout << "No" << endl;
}