import re


def is_valid(number):
    """
    Check if number is roman

    :param number: string to check
    :type number: str

    :return: True or False
    :rtype: bool
    """
    return re.match(
        r"^(M{0,3})(D?C{0,3}|C[DM])(L?X{0,3}|X[LC])(V?I{0,3}|I[VX])$", number
    )