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

int main(){
  int a, b, c, d;
  cin >> a >> b >> c >> d;
  int ta, ao;
  ta = a/b+1;
  ao = c/d+1;
  if(ta>ao) cout << "Yes" << endl;
  else cout << "No" << endl;
  return 0;
}
