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#!/usr/bin/python3
# Challenge 017
#
# Task #1
# Create a script to demonstrate Ackermann function. The Ackermann function is
# defined as below, m and n are positive number:
#
# A(m, n) = n + 1 if m = 0
# A(m, n) = A(m - 1, 1) if m > 0 and n = 0
# A(m, n) = A(m - 1, A(m, n - 1)) if m > 0 and n > 0
#
# Example expansions as shown in wiki page.
#
# A(1, 2) = A(0, A(1, 1))
# = A(0, A(0, A(1, 0)))
# = A(0, A(0, A(0, 1)))
# = A(0, A(0, 2))
# = A(0, 3)
# = 4
import sys
def A(m, n):
if m==0:
return n+1
elif m>0 and n==0:
return A(m-1, 1)
elif m>0 and n>0:
return A(m-1, A(m, n-1))
print(A(*[int(x) for x in sys.argv[1:3]]))
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