题解 | #汽水瓶#

# 递归
import sys
lists=[]
for line in sys.stdin:
    line = line.rstrip("\n")
    lists.append(line)
del lists[-1]
def f(x):
    drink=x//3
    global all_drink
    all_drink+=drink
    ping=x%3+drink
    if ping==0 or ping==1:
        return all_drink
    else:
        if ping==2:
            ping+=1
        else:
            pass
        return f(ping)
           
for i in lists:
    all_drink=0
    print(f(int(i)))