题解 | #汽水瓶#

import sys

input_list = []
while True:
    line = sys.stdin.readline().strip()
    if line == "0":
        break
    input_list.append(line)


def battle(n):
    if n <= 1:
        return 0
    elif n == 2:
        return 1
    else:
        x = n % 3
        y = n // 3
        return y + battle(x + y)


for n in input_list:
    num = battle(int(n))
    print(num)