string hackerrankInString(string s) {
  string refS = "hackerrank";
  size_t preIt = 0;
  for(size_t i = 0; i < refS.length(); i++) {
    size_t it = s.find_first_of(refS[i], preIt);
    if(it == string::npos)
      return "NO";
    preIt = s.find_last_of(refS[i], it) + 1;
  }
  return "YES";
}