题解 | #汽水瓶#

flag = 1
list=[]
while flag:
    count = 0
    n = int(input())
    if n != 0:
        while n // 3 > 0:
            count += n//3
            n=n//3+n%3
        if n==2:
            count += 1
        list.append(count)
    else:
        flag = 0
for i in list:
    print(i)