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 CSharp_AtCoder
{
    class Program
    {
        static int N;

        static bool Check753(string str)
        {
            if (str.Contains("7") && str.Contains("5") && str.Contains("3"))
            {
                return true;
            }
            else return false;
        }

        static int Solve(int max_cnt, int cnt, string str_753)
        {
            if(cnt >= max_cnt)
            {
                if (int.Parse(str_753) <= N && Check753(str_753)) return 1;
                else return 0;
            }

            return Solve(max_cnt, cnt + 1, str_753 + "7")
                 + Solve(max_cnt, cnt + 1, str_753 + "5")
                 + Solve(max_cnt, cnt + 1, str_753 + "3");
        }

        static void Main(string[] args)
        {
            N = int.Parse(Console.ReadLine());

            int sum = 0;
            for(int i = 3; i <= 9; i++)
            {
                sum += Solve(i, 0, "");
            }

            Console.WriteLine(sum);
        }
    }
}