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)


//Stack Over Flow Recursive

using System;
using System.Collections;
using System.Collections.Generic;
namespace Ccs
{
    class Program
    {
        static void Main(string[] args)
        {
            var n = long.Parse(Console.ReadLine());

            var pr = new Program();

            Console.WriteLine(pr.Rec(0,n));
        }

        private const String sgs = "357";
        private bool Is_sgs(String s)
        {

            bool is_sgs_ = true;
            for (int i = 0; i < sgs.Length; ++i)
                is_sgs_ &= s.Contains(sgs[i].ToString());

            return is_sgs_;
        }

        private bool Is_sgs(long n)
        {
            return this.Is_sgs(n.ToString());
        }

        
        private long Rec(long x, long n)
        {
            //            var x = int.Parse(s);
            if (n < x)
                return 0;
            //            if (Is_sgs(x))
            //                Console.WriteLine(x);

            long ret = Is_sgs(x) ? 1 : 0;

            foreach ( char c in sgs)
                ret += Rec(x * 10 + int.Parse( c.ToString() ), n);

            return ret;
        }
        
    }
}