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)

import scala.io.{StdIn => in}
import scala.collection.{mutable => mu}

object Main extends App {
  val s = in.readLine
  val digit = s.size
  val N = s.toInt

  def dfsEnum(d:Int, n:Int):Int = {
    // d進 n個列挙
    val enum = Array.ofDim[Int](n)
    var ret = 0
    var terms = true //仮変数 実装時置き換える
  
    def evalute():Unit = {
      if(!n753.indices.forall(i => enum.exists(_ == n753(i)))) return
      val num = enum.mkString.toInt
      if(num <= N) {
        ret += 1
        // println(num)
      }
    }
  
    def dfs(cnt:Int):Unit = {
      if(cnt == n) evalute
      else {
        for(i <- n753) {
          enum(cnt) = i
          dfs(cnt+1)
        }
      }
    }
  
    dfs(0)
    ret
  }

  val n753 = Array(3,5,7)
  val ans = (3 to digit).map(i => dfsEnum(n753.size, i)).sum
  println(ans)
}