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: Wrong Answer)

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

class Program
{
  static void Main(string[] args)
  {
    var n = Int32.Parse(Console.ReadLine());

    var shichigosanNums = new List<int>();
    for (var digit = 3; digit < 10; digit++)
    {
      for (var i = 0; i < Math.Pow(3, digit); i++)
      {
        var s = "";
        for (var d = 0; d < digit; d++)
        {
          var di = 0;
          if (d == 0)
          {
            di = i % 3;
          }
          else
          {
            di = i % (int)Math.Pow(3, d + 1) / (int)Math.Pow(3, d);
          }
          if (di == 0)
          {
            s += 3;
          }
          else if (di == 1)
          {
            s += 5;
          }
          else if (di == 2)
          {
            s += 7;
          }
        }
        if (s.Contains('7') && s.Contains('5') && s.Contains('3'))
        {
          shichigosanNums.Add(Int32.Parse(string.Concat(s.Reverse())));
        }
      }
    }

    var c = 0;
    foreach (var shichigosanNum in shichigosanNums)
    {
      if (shichigosanNum < n)
      {
        c++;
      }
      else
      {
        break;
      }
    }
    Console.WriteLine(c);
  }
}