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;

class Program
{
    static string s = Console.ReadLine();
    static List<int> list = new List<int>();

    static void Main()
    {
        Dfs("");
        int n = int.Parse(s);
        list.Sort();
        for (int i = list.Count - 1; i >= 0; i--)
        {
            if (list[i] > n) list.RemoveAt(i);
            else break;
        }

        Console.WriteLine(list.Count);
    }

    static void Dfs(string x)
    {
        if (Check(x)) list.Add(int.Parse(x));
        if (x.Length < s.Length)
        {
            Dfs(x + '3');
            Dfs(x + '5');
            Dfs(x + '7');
        }
    }

    static bool Check(string t)
    {
        bool[] sign = new bool[3];
        for (int i = 0; i < t.Length; i++)
        {
            switch (t[i])
            {
                case '7':
                    sign[0] = true;
                    break;
                case '5':
                    sign[1] = true;
                    break;
                case '3':
                    sign[2] = true;
                    break;
                default:
                    return false;
                    break;
            }
        }
        if (sign[0] == true && sign[1] == true && sign[2] == true)
            return true;
        else return false;
    }
}