from typing import Generic, TypeVar

class UnwrapException(Exception):
    def __init__(self, *args: object) -> None:
        super().__init__(*args)

T = TypeVar("T")
E = TypeVar("E")

class Result(Generic[T, E]):
    def __init__(self) -> None:
        super().__init__()

    def ok(self) -> bool:
        raise NotImplementedError()

    def value(self) -> T:
        raise NotImplementedError()

    def error(self) -> E:
        raise NotImplementedError()

class Ok(Result[T, E]):
    def __init__(self, value: T) -> None:
        super().__init__()
        self.__value = value

    def ok(self) -> bool:
        return True

    def value(self) -> T:
        return self.__value

    def error(self) -> E:
        raise UnwrapException("cannot unwrap error of ok result")

class Err(Result[T, E]):
    def __init__(self, error: E) -> None:
        super().__init__()
        self.__error = error

    def ok(self) -> bool:
        return False

    def value(self) -> T:
        raise UnwrapException("cannot unwrap value of error result")

    def error(self) -> E:
        return self.__error