"""This module contains a code example related to

Think Python, 2nd Edition
by Allen Downey
http://thinkpython2.com

Copyright 2015 Allen Downey

License: http://creativecommons.org/licenses/by/4.0/
"""

from __future__ import print_function, division


def ackermann(m, n):
    """Computes the Ackermann function A(m, n)

    See http://en.wikipedia.org/wiki/Ackermann_function

    n, m: non-negative integers
    """
    if m == 0:
        return n+1
    if n == 0:
        return ackermann(m-1, 1)
    return ackermann(m-1, ackermann(m, n-1))


print(ackermann(3, 4))