import random
from sys import argv

def hall_old():
    choices = [0]*3
    choices[random.randint(0,2)] = 1
    guess = random.randint(0,2)
    reveal = (random.randint(1,2)+guess)%3 # This gives ~55%
    reveal = 2 - guess # This gives ~44%
    if choices[reveal]==1:
        return hall()
    return choices[3-guess-reveal]==1

def hall(): # This gives 66%
    choices = [0]*3
    choices[random.randint(0,2)] = 1
    guess = 0
    for i in range(1,3):
        if choices[i]==0:
            reveal = i
            break
    return choices[3-guess-reveal]==1

def main():
    times = int(argv[1]) # times game is played
    correct = 0
    for i in range(0, times):
        if hall_old():
            correct += 1
    print str(correct * 100 / times) + '%'

main()