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)

def f(*a)
  return a if a.max > @max
  a << a.map { |aa| [aa * 10 + 3, aa * 10 + 5, aa * 10 + 7]}.flatten.uniq.map { |aa| f(aa) }.flatten.uniq
end

@max = gets.chomp.to_i

ll = f(3, 5, 7)
count = 0
ll.flatten!
ll.reject! { |n| n > @max  }
ll.each do |n|
  n = n.to_s
  if n.count('3') >= 1 && n.count('5') >= 1 && n.count('7') >= 1
    count += 1 
  end
end

puts count