"""

Name: fib - Fibonacci number machine

Description: Recursive and DP-based calculation of Fibonacci numbers.

Author: Eugen Sawin <sawine@me73.com>

"""

def main():

    args = parse_args()

    if args.d:

        fun = fib_dynamic

    else:

        fun = fib

    print fun(args.n)

def fib(n):

    if n > 1:

        return fib(n-1) + fib(n-2)

    else:

        return n

def fib_dynamic(n):

    f = (0, 1)

    for i in xrange(2, n + 1):

        f = (f[1], sum(f))

    if n < 1:

        return n

    else:

        return f[1]

from argparse import ArgumentParser

def parse_args():

    parser = ArgumentParser(description='Returns the Fibonacci number for a given number n.')

    parser.add_argument('n', type=int, help='Fib(n)')

    parser.add_argument('-d', action='store_true', help='dynamic programming')

    return parser.parse_args()

if __name__ == "__main__":

    main()