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 c
{
    static void Main()
    {
        int n = int.Parse(Console.ReadLine());
        var list = new List<int>();
        Search(9, "", ref list);
        list = list.OrderBy(f => f).ToList();
        int ans = 0;
        for (int i = 0; i < list.Count(); i++)
        {
            if (list[i] <= n) ans++;
            else break;
        }
        Console.WriteLine(ans);
    }
    static void Search(int n, string s, ref List<int> list)
    {
        if (n + 1 == s.Length) return;
        else if (s.Distinct().Count() == 3) list.Add(int.Parse(s));
        Search(n, "3" + s, ref list);
        Search(n, "5" + s, ref list);
        Search(n, "7" + s, ref list);
    }
}