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 Scala (2.11.7) (judge verdict: Accepted)

object Main extends App {
  val in = new java.util.Scanner(System.in)
  val N = in.next.map(_ - '0').toList

  implicit class ComparableIntList(val l: List[Int]) extends AnyVal {
    def <=(o: List[Int]): Boolean = {
      if (l.size < o.size) true
      else if (l.size > o.size) false
      else l.zip(o).find(t => t._1 != t._2).fold(true)(t => t._1 <= t._2)
    }
  }

  def valid(l: List[Int]): Boolean = List(3, 5, 7).forall(n => l.contains(n))

  def dfs(l: List[Int], fixed: Boolean): Int = {
    Array(3, 5, 7).map{i =>
      val next = i :: l
      if (next <= N) {
        if (fixed || valid(next)) 1 + dfs(next, fixed)
        else dfs(next, false)
      } else 0
    }.sum
  }

  println(dfs(Nil, false))
}