# Computes n factorial recursively
def factorial(n):
    if n == 0:
        return 1
    return n * factorial(n - 1)

# Computes the sum of a list of numbers
def sum_list(l):
    if len(l) == 0:
        return 0
    return l[0] + sum_list(l[1:])

# Computes the greatest common denominator of m and n
# Uses euclid's algorithm
def gcd(m, n):
    if n == 0:
        return m
    return gcd(n, m % n)