def is_pow_2(n):

    bin_count = 0

    while n > 0:

        if n % 2 == 1:

            bin_count += 1

        if bin_count > 1:

            return False

        n /= 2

    return bin_count == 1

def collatz_pow_2(n):

    if n == 1: return 4

    if n == 2: return 4

    collatz_pow_2 = []

    while n > 2:

        print n, 

        if is_pow_2(n):

            collatz_pow_2.append(n)

        if n % 2:

            n = n * 3 - 1

        else:

            n /= 2 

    return max(collatz_pow_2)

import sys

collatz_pow_2(int(sys.argv[1]))