from enum import Enum
from typing import override


class Tern(Enum):
    N = -1
    U = 0
    Y = 1

    @override
    def __str__(self):
        if self.value == -1:
            return "0"
        if self.value == 1:
            return "1"
        return "N"

    @classmethod
    def from_string(cls, s: str) -> "Tern":
        if s == "N":
            return Tern.U
        if s == "0":
            return Tern.N
        if s == "1":
            return Tern.Y
        return cls[s]