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 java.util.Scanner

object Main {
  def main(args: Array[String]): Unit = {
    val sc = new Scanner(System.in)
    val n = sc.nextLine
    var acc = scala.collection.mutable.ArrayBuffer[String]()

    def go(n: Int, s: String): Unit = {
      if (n == 0) {
        acc += s
      } else {
        go(n - 1, s + "3")
        go(n - 1, s + "5")
        go(n - 1, s + "7")
        go(n - 1, s + "0")
      }
    }

    go(n.length, "")
    println(acc.map(_.toInt).filter(_ <= n.toInt).count(s => s.toString.distinct.length == 3 & !s.toString.contains("0")))
  }
}