#!/usr/bin/env python

import sys
import os

"""
Author  : flo
date    : 2016.12.09
Purpose : example of finding the minimal number of AVL tree Node 
        : equation: S(h) = S(h-1) + S(h-2) + 1
Comments: it is recursive function messiness
        : first rename this file from avlTree2.txt to avlTree.py
        : that value 6 is needed, it is the height of a AVL tree starting with 0
        : S(0) = 1; S(1) = 2
        : if you can crank 'python avlTree2.py 50' or 100 within an hour,
        : that is one extremely Powerful PC, you got there.
usage   : python avlTree2.py 6
"""


def prtAVLCompute(n):
    if n==0:
        return 1
    elif n==1:
        return 2
    else:
        return prtAVLCompute(n-1)+prtAVLCompute(n-2) + 1
            

def main():
    value = int(sys.argv[1])
    print prtAVLCompute(value)


# added proper main function
if __name__ == "__main__":
    main()