import sys
lines = []
for line in sys.stdin:
    a=int(line)
    if a!=0:
        lines.append(a)  

lenLine = len(lines)
        
def MaxBottleNum(Num):
    rest = (Num%3)
    n = (Num//3)
    New_Num = n + rest
    while((New_Num)>=3):
        n +=(New_Num//3)
        rest1 = New_Num%3
        New_Num = rest1 + (New_Num//3)
    if New_Num == 2:
        n += 1
    return n
for i in range(lenLine):
    num = lines[i]
    print(MaxBottleNum(num))