from enum import IntEnum
from typing import Optional

class Difficulty(IntEnum):
    EASY = 0
    NORMAL = 1
    HARD = 2

values = [
    Difficulty.EASY,
    Difficulty.NORMAL,
    Difficulty.HARD]

def format(difficulty: Difficulty) -> str:
    if difficulty == Difficulty.EASY:
        return 'Easy'
    elif difficulty == Difficulty.NORMAL:
        return 'Normal'
    elif difficulty == Difficulty.HARD:
        return 'Hard'

def parse(string: str) -> Optional[Difficulty]:
    if string == 'Easy':
        return Difficulty.EASY
    elif string == 'Normal':
        return Difficulty.MIDDLE
    elif string == 'Hard':
        return Difficulty.HARD
    else:
        return None