#-- The Computer Language Shootout

#-- http://shootout.alioth.debian.org/

#-- contributed by Tobias Polzin, translated from Mike Pall's Lua program

#-- modified by Josh Goldfoot to use ifs for the complement routine

import sys

N = int(sys.argv[1])

first = None

second = None

meetings = 0

RED, BLUE, YELLOW = xrange(1,4)

#-- Create a very social creature.

def creature(me):

    global N, first, second, meetings

    met = 0

    while 1:

        #-- Meet another creature.

        #-- Wait until meeting place clears.

        while second:

            yield None

        other = first

        if other:

            #-- Hey, I found a new friend!

            second = me

        else:

            # -- Sniff, nobody here (yet).

            if N <= 0:

                #-- Uh oh, the mall is closed.

                meetings += met

                yield None

                # The mall was closed, so everyone is faded.

                raise StopIteration

            N -= 1

            first = me

            while not second:

                yield None #-- Wait for another creature.

            other = second

            first = None

            second = None

            yield None

        # perform meeting

        met += 1

        if me != other:

            if me == BLUE:

                me = other == RED and YELLOW or RED

            elif me == RED:

                me = other == BLUE and YELLOW or BLUE

            elif me == YELLOW:

                me = other == BLUE and RED or BLUE

#-- Trivial round-robin scheduler.

def schedule(threads):

    global meetings

    try:

        while 1:

            for thread in threads:

                thread.next()

    except StopIteration:

        return meetings

def main():

    #-- A bunch of colorful creatures.

    threads = [

        creature(BLUE),

        creature(RED),

        creature(YELLOW),

        creature(BLUE) ]

    print schedule(threads)

main()