import re


def normalize_number(phone_number):
    pattern = re.compile("([\+]*[1][ -])*(\(*[2-9][0-9][0-9]\)*)[- .]([0-9][0-9][0-9])[ -.]([2-9][0-8][0-9][0-9])")

    if not pattern.match(phone_number):
        raise ValueError("Ungültige Telefonnummer")

    normalized_number = re.sub("\+*\(*\)*", "", phone_number)
    normalized_number = re.sub("[ .]", "-", normalized_number)

    if normalized_number[0] != str(1):
        normalized_number = "1-" + normalized_number

    return normalized_number