#include <bits/stdc++.h>
using namespace std;
 
int main() {
  int A, B, C, D;
  cin >> A >> B >> C >> D;
  
  string res;
  
  for (int i = 1; i <= 200; i++) {
    A = A - D*( (i+1) % 2 );
    C = C - B*( (i) % 2 );
    
    if (A <= 0) {
      res = "No";
      cout << res << endl;
      return 0;
      
    } else if (C <= 0){
      res = "Yes";
      cout << res << endl;
      return 0;
    }
  }
  
}