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.chomp
def dfs(num, array)
  # 入力値よりも桁数が大きくならない範囲で処理
  if num.length <= N.length
    array << num unless num.empty? # 初期値避け
    dfs(num + "3", array)
    dfs(num + "5", array)
    dfs(num + "7", array)
  end
  if num.empty?
    array
  end
end
array = dfs("", [])
# 入力値よりも小さく、3, 5, 7を含むものだけ残して個数を出す
puts array.map { |num| num.to_i <= N.to_i && num.include?("3") && \
  num.include?("5") && num.include?("7") ? num : nil }.compact.count