class Encryptor{
  static String charPool = "AKFLDJAHSPIWUROCNMZX";

  static String intToString(int input){
    String output = "";
    for(int i=0; i < input.toString().length; i++){
      output += charPool[int.parse(input.toString()[i])];
    }

    int luckyNumber = GetLuckyNumber(input);

    String lastLetter = charPool[luckyNumber];

    return output + lastLetter;
  }

  static int stringToInt(String input){
    String output = "";
    for(int i=0; i < input.length-1; i++){
      for(int j=0; j < charPool.length; j++){
        if(charPool[j] == input[i]){
          output += j.toString();
          break;
        }
      }
    }

    String lastChar = input[input.length-1];

    int outputInt = int.parse(output);
    String luckyChar = charPool[GetLuckyNumber(outputInt)];
    bool validated = luckyChar == lastChar;

    if(validated){
      return outputInt;
    }else{
      print("Error validating User ID, expected $luckyChar got $lastChar");
      return -1;
    }
  }

  static int GetLuckyNumber(int input){
    int luckyNumber = input;

    while(luckyNumber >= 10){
      int val = 0;
      for(int i=0; i < luckyNumber.toString().length; i++){
        val+= int.parse(luckyNumber.toString()[i].toString());
      }

      luckyNumber = val;
    }

    return luckyNumber;
  }
}