import 'dart:io';

void main(List<String> args){
  List<int> N = stdin.readLineSync().split(' ').map((i) => int.parse(i)).toList();
  int takahashi = C/B;
  int aoki = A/D;
  if(C%B!=0) takahashi = takahashi + 1;
  if(A%D!=0) aoki = aoki + 1;
  if(takahashi > aoki) print("No");
  else print"Yes");
}