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: Wrong Answer)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ABC114
{
    class Program
    {
        static int n;
        static sbyte p;
        static void Main(string[] args)
        {
            n = int.Parse(Console.ReadLine());
            p = (sbyte)(Math.Log10(n) + 1);
            int ans = Func(p, 0,0);
            Console.WriteLine(ans);
        }
        static int Func(sbyte depth,int sum,byte flag)
        {
            if (sum > n) { return 0; }
            int c = (int)Math.Pow(10, depth - 1);
            if (depth == 0) { if (sum <= n && flag == 7) { return 1; } else { return 0; } }
            return Func((sbyte)(depth - 1), sum, 0) + Func((sbyte)(depth - 1), sum + c * 3, (byte)(flag|4)) + Func((sbyte)(depth - 1), sum + c * 5,(byte)(flag|2)) + Func((sbyte)(depth - 1), sum + c * 7,(byte)(flag|1));
        }
    }
}