N = gets.to_i
D = N.to_s.size

def f(n)
  return false if n <= 0
  return false if n % 3 != 0

  digits = n.digits

  return false if digits.size <= 1

  digits.combination(2).all? { |a, b| (a + b) % 3 == 0 }
end

ans = 0

(1..[N, 99].min).each do |n|
  ans += 1 if f(n)
end

$cnt = 0
$checked = Hash.new(false)

def dfs(sum, base, depth)
  return if D < depth

  if depth >= 3 && 100 <= sum && sum <= N && !$checked[sum]
    $checked[sum] = true
    $cnt += 1
  end

  [0, 3, 6, 9].each do |n|
    s = sum + base * n

    dfs(s, base * 10, depth + 1)
  end
end

dfs(0, 1, 0)
puts $cnt + ans