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;
using System.Collections.Generic;

class Program
{
    static long F(long n, long N)
    {
        if (n > N)
            return 0;
        else
        {
            string s = n.ToString();
            uint r = 0;
            for(int i = 0; i < s.Length; i++)
            {
                if (s[i] == '7')
                    r |= 1;
                if (s[i] == '5')
                    r |= 2;
                if (s[i] == '3')
                    r |= 4;
            }
            return F(10 * n + 7, N) + F(10 * n + 5, N) + F(10 * n + 3, N) + (r == 7 ? 1 : 0);
        }
    }

    public static void Main()
    {
        long N = long.Parse(Console.ReadLine());
        Console.WriteLine(F(0,N));
    }
}