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.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Atcoder
{
    class Program
    {
        static void Main(string[] args)
        {

            int n = int.Parse(Console.ReadLine());

            int output = 0;
            string value = "357";

            while (true)
            {
                if (n < long.Parse(value)) break;
                if (isSuitable(value))
                {
                    output++;
                }
                value = nextnumber(value);
            }
            Console.WriteLine(output);
            ;
        }

        static bool isSuitable(string shichigosan)
        {
            if (shichigosan.Contains("3") && shichigosan.Contains("5") && shichigosan.Contains("7"))
                return true;
            else return false;

        }

        static string nextnumber(string shichigosan)
        {
            string output = shichigosan;

            if (shichigosan.Length == 0)
            {
                return "3";
            }
            if (shichigosan[shichigosan.Length - 1] == '3')
            {
                return output.Substring(0, output.Length - 1) + '5';
            }
            if (shichigosan[shichigosan.Length - 1] == '5')
            {
                return output.Substring(0, output.Length - 1) + '7';
            }
            if (shichigosan[shichigosan.Length - 1] == '7')
            {
                return nextnumber(output.Substring(0, output.Length -1 )) + '3';
            }
            return "";
        }

    }
}