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 C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Linq;
using System.Collections.Generic;

class Cmondai
{
    static void Main()
    {
        var N = Int64.Parse(Console.ReadLine());
        var nKeta = Math.Log10(N)+1;
        var max = (int)Math.Pow(3,9);
        var list = new List<string>();
        var ans = 0;
        for (int i=0;i<nKeta;++i)
        {
            for (int j=0;j<Math.Pow(3,i+1);++j) {

                var num = j;
                var keta = 0;
                var amari = 0;
                var suji = "";

                while (keta<i+1) {
                    amari = num % 3;
                    switch (amari)
                    {
                        case 0: suji += "3"; break;
                        case 1: suji += "5"; break;
                        case 2: suji += "7"; break;
                    }
                    num /= 3;
                    keta++;
                }
                if (Int64.Parse(suji) <= N && suji.Contains("3") && suji.Contains("5") && suji.Contains("7")) ans++;
            }
        }
        Console.WriteLine(ans);
    }
}