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.collection.mutable.ArrayBuffer
object Main extends App {
  val in = new java.util.Scanner(System.in)
  val (size, n) = {
    val n = in.next
    (n.size, n.toInt)
  }

  val candidates = ArrayBuffer[String]()
  def dfs(s: String): Unit = {
    Array("3", "5", "7").foreach{d =>
      val next = d + s
      if (next.size <= size) {
        candidates += next
        dfs(next)
      }
    }
  }

  dfs("")
  println(candidates.filter(c => c.toInt <= n && c.distinct.size == 3).size)
}