def fact(n):
    """Calculates n!"""
    if n == 0:
        return 1
    else:
        return n * fact(n - 1)

def sum_digits(n):
    """Calculates the sum of the digits `n`
    >>> sum_digits(8)
    8
    >>> sum_digits(18)
    9
    >>> sum_digits(2018)
    11
    """
    if n < 10:
        return n
    else:
        all_but_last, last = n // 10, n % 10
        return sum_digits(all_but_last) + last

def count_up(n):
    """Prints the numbers from 1 to n. Assume `n` is positive.
    >>> count_up(1)
    1
    >>> count_up(2)
    1
    2
    >>> count_up(4)
    1
    2
    3
    4
    """
    if n == 1:
        print(1)
    else:
        count_up(n - 1)
        print(n)

def is_even(n):
    if n == 0:
        return True
    return is_odd(n - 1)

def is_odd(n):
    if n == 0:
        return False
    return is_even(n - 1)

def has_eight(n):
    """Check is the number contains an 8.
    >>> has_eight(8)
    True
    >>> has_eight(18)
    True
    >>> has_eight(123456790)
    False
    >>> has_eight(181)
    True
    """
    if n == 0:
        return False
    all_but_last, last = n // 10, n % 10
    return last == 8 or has_eight(all_but_last)