def sum_multiples(n: int) -> int:
    """
    Get sum of multiples 3 and 5 below :param: n.

    Example:
        n = 10 -> 3 + 5 + 6 + 9 = 23
    """
    return sum(x for x in range(n) if x % 5 == 0 or x % 3 == 0)