#!/usr/bin/python
# $Id: fibo.python,v 1.2 2000/12/24 19:10:50 doug Exp $
# http://www.bagley.org/~doug/shootout/

import sys

def fib(n):
    if (n < 2):
        return(1)
    return( fib(n-2) + fib(n-1) )

def main():
    N = int(sys.argv[1])
    #sys.setrecursionlimit(3000)
    print fib(N)

main()