#Aufgabe 4a
import re

def number_normalize(a):
    number = re.fullmatch(r'((\+1)|1)?[\s\-\.\(]?[2-9][0-8][0-9][)]?[\s\-\.]?[2-9][0-9][0-9][\s\-\.]?[0-9]{4}', a)
    if (number == None):
        raise ValueError("Ungültige Telefonnummer!")
    else:
        a = a.replace(' ', '')
        a = a.replace('+', '')
        a = a.replace('-', '')
        a = a.replace('.', '')
        a = a.replace('(', '')
        a = a.replace(')', '')
        if(a[0] == '1'):
            a = '{}-{}-{}-{}'.format(a[0:1], a[1:4], a[4:7], a[7:11])
        else:
            a = '1-{}-{}-{}'.format(a[0:3], a[3:6], a[6:10])
        return a