n=input()
if len(n) < 3:
    print(0)
    exit()
if len(n)%3 != 0:
    print('9'*(len(n)//3))
    exit()
    
n=n[:len(n)//3]

for i in range(1,10**5 + 1):
    if i > int(n):
        break
    ans = i
print(ans)