def hello(x=None) -> str:
    s = "Hello"
    if x:
        s += f", {x}"

    return s + "!"


def int_to_roman(x: int) -> str:
    match = [
        (1000, "M"),
        (900, "CM"),
        (500, "D"),
        (400, "CD"),
        (100, "C"),
        (90, "XC"),
        (50, "L"),
        (40, "XL"),
        (10, "X"),
        (9, "IX"),
        (5, "V"),
        (4, "IV"),
        (1, "I"),
    ]

    lst = []
    for num, text in match:
        while x >= num:
            x -= num
            lst.append(text)

    return "".join(lst)


def longest_common_prefix(x: list[str]) -> str:
    if not x:
        return ""

    s = x[0].strip()
    ind = 0
    flag = False

    while ind < len(s):
        for word in x:
            word = word.strip()
            if len(word) <= ind or word[ind] != s[ind]:
                flag = True
                break
        if flag:
            break

        ind += 1

    if ind == -1:
        return ""

    return s[:ind]


class BankCard:
    def __init__(self, total_sum: int, balance_limit: int = -1) -> None:
        self.total_sum = total_sum
        self.balance_limit = balance_limit

    @property
    def balance(self) -> int:
        if self.balance_limit == 0:
            raise ValueError("Balance check limits exceeded.")

        self.balance_limit -= 1

        return self.total_sum

    def put(self, sum_put: int):
        self.total_sum += sum_put
        print(f"You put {sum_put} dollars.")

        return self

    def __add__(self, other):
        if self.balance_limit == -1 or other.balance_limit == -1:
            new_balance_limit = -1
        else:
            new_balance_limit = max(self.balance_limit, other.balance_limit)

        return type(self)(self.total_sum + other.total_sum, new_balance_limit)

    def __call__(self, sum_spent: int) -> None:
        if self.total_sum < sum_spent:
            raise ValueError(f"Not enough money to spend sum_spent dollars.")

        self.total_sum -= sum_spent
        print(f"You spent {sum_spent} dollars")

        return

    def __str__(self) -> str:
        return "To learn the balance call balance."


def primes():
    pr = 2

    while True:
        flag = False

        for n in range(2, int(pr**0.5) + 1):
            if pr % n == 0:
                flag = True
                break

        if not flag:
            yield pr

        pr += 1