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 {
  def main(args: Array[String]): Unit = {
    solve
  }

  def solve(): Unit = {
    import scala.io.StdIn._
    val n = readLong

    val nums = new ArrayBuffer[String]()

    def dfs(x: String): Unit = {
      if (!x.isEmpty && x.toLong > n) {
        // n を超えた数は以降の処理は対象外
        return
      }

      if (x.toCharArray.distinct.size == 4) {
        // 3, 5, 7 を少なくとも一つ含む場合は753数（頭の0があるので+1）
        nums += x
      }
      // 3, 5, 7を後ろにくっつけて再帰
      dfs(x + "3")
      dfs(x + "5")
      dfs(x + "7")
    }

    dfs("0")
    println(nums.size)
  }
}