Source code for kyu_7.factorial.factorial

"""
Solution for -> Factorial.

Created by Egor Kostan.
GitHub: https://github.com/ikostan
"""




def factorial(n: int) -> int:
    """
    Factorial function.

    A function to calculate factorial for a given input.
    If input is below 0 or above 12 throw an exception
    of type ValueError (Python).
    :param n:
    :return:
    """
    if n < 0 or n > 12:
        raise ValueError(f'Invalid input: {n}')

    result: int = 1
    while n > 0:
        result *= n
        n -= 1

    return result