Problem:
Score : 300 points

Problem Statement

You are given an integer N. Among the integers between 1 and N (inclusive), how many Shichi-Go-San numbers (literally "Seven-Five-Three numbers") are there?

Here, a Shichi-Go-San number is a positive integer that satisfies the following condition:

When the number is written in base ten, each of the digits 7, 5 and 3 appears at least once, and the other digits never appear.

Constraints

1 \leq N < 10^9

N is an integer.

Input

Input is given from Standard Input in the following format:

N

Output

Print the number of the Shichi-Go-San numbers between 1 and N (inclusive).

Sample Input 1

575

Sample Output 1

4

There are four Shichi-Go-San numbers not greater than 575: 357, 375, 537 and 573.

Sample Input 2

3600

Sample Output 2

13

There are 13 Shichi-Go-San numbers not greater than 3600: the above four numbers, 735, 753, 3357, 3375, 3537, 3557, 3573, 3575 and 3577.

Sample Input 3

999999999

Sample Output 3

26484

Solution in Ruby (2.3.3) (judge verdict: Accepted)

N = gets.to_i
digits = N.to_s.size

def dfs(digits_size, digits = [])
  return [digits] if digits.size == digits_size
  [7, 5, 3].flat_map do |n|
    dfs(digits_size, digits + [n])
  end
end

ans = 0
(3..digits).each do |d|
  dfs(d).each do |list|
    is_ok = list.join('').to_i <= N &&
      list.count { |n| n == 7 } >= 1 &&
      list.count { |n| n == 5 } >= 1 &&
      list.count { |n| n == 3 } >= 1
    ans += 1 if is_ok
  end
end
puts ans