from collections import *
from itertools import *
from functools import *
from heapq import *
import sys,math
input = sys.stdin.readline

N = int(input())

ans = 0
for i in range(1,100000):
    s = str(i)
    if s[0]=='0':
        continue
    s = int(3*s)
    if s<=N:
        ans += 1
    else:
        break
print(ans)