import sys
import pypyjit
import itertools
import heapq
import math
from collections import deque, defaultdict
import bisect

input = sys.stdin.readline
sys.setrecursionlimit(10 ** 6)
pypyjit.set_param('max_unroll_recursion=-1')


def index_lt(a, x):
    'return largest index s.t. A[i] < x or -1 if it does not exist'
    return bisect.bisect_left(a, x) - 1


def index_le(a, x):
    'return largest index s.t. A[i] <= x or -1 if it does not exist'
    return bisect.bisect_right(a, x) - 1


def index_gt(a, x):
    'return smallest index s.t. A[i] > x or len(a) if it does not exist'
    return bisect.bisect_right(a, x)


def index_ge(a, x):
    'return smallest index s.t. A[i] >= x or len(a) if it does not exist'
    return bisect.bisect_left(a, x)


N = int(input())
if N < 100:
    print(N // 3 - 3)
else:
    cands = []

    def dfs(s):
        if len(s) >= 3:
            cands.append(int(s))
        if len(s) == 9:
            return
        for n in [0, 3, 6, 9]:
            if len(s) == 0 and n == 0:
                continue
            dfs(s + str(n))
    dfs('')
    cands.sort()
    print(30 + index_le(cands, N) + 1)