#coding: utf-8
"""
http://www.zhihu.com/question/21503093

a set of cards including 52 cards tagged from 1 to 52, no joker cards
"""

import copy

def perfect_shuffle(cards):
    size = len(cards)
    left, right = cards[0:size/2], cards[size/2:]
    new_cards = []

    for i in range(size/2):
        new_cards.append(left[i])
        new_cards.append(right[i])

    return new_cards


def main():
    cards = range(1, 53)
    shuffle_times = 0
    old_cards = copy.deepcopy(cards)
    new_cards = []

    while True:
        new_cards = perfect_shuffle(old_cards)
        shuffle_times += 1

        if new_cards == cards:
            break

        old_cards = copy.deepcopy(new_cards)

    print shuffle_times


if __name__ == '__main__':
    main()