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.IO;

class Program
{

    public static void Main()
    {
        long N = int.Parse(Console.ReadLine());

        //たくさん確保
        long[] a = new long[1000000];

        a[0] = 3;
        a[1] = 5;
        a[2] = 7;

        for (int i = 0; a[3 * (i - 1) + 5] <= N; i++)
        {
            a[3 * i + 3] = a[i] * 10 + 3;
            a[3 * i + 4] = a[i] * 10 + 5;
            a[3 * i + 5] = a[i] * 10 + 7;
//            (a[3 * i + 3],
//                a[3 * i + 4],
//                a[3 * i + 5]) = sgs(a[i]);
        }

        int count = 0;

        //全てのa[i]に対して、条件を満たすか調べる
        for (int i = 0; a[i] <= N; i++)
        {
            //            Console.WriteLine(a[i]);
            int check3 = 0;
            int check5 = 0;
            int check7 = 0;
            long tmp;

            tmp = a[i];

            //全ての桁に対して、数値を調べる
            for (int j = 0; j < 10; j++)
            {
                //                Console.WriteLine(tmp);
                if (tmp % 10 == 3)
                {
                    check3++; tmp /= 10;
                }
                else if (tmp % 10 == 5)
                {
                    check5++; tmp /= 10;
                }
                else if (tmp % 10 == 7)
                {
                    check7++; tmp /= 10;
                }

            }

            /*            Console.WriteLine("{0} {1} {2} {3}",
                                check3,
                                check5,
                                check7,
                                N);
            */
            if (check3 > 0
                && check5 > 0
                && check7 > 0
                && a[i] <= N)
            {
                count++;

            }
        }

        Console.WriteLine(count);
        //        (a[3], a[4], a[5]) = sgs(a[0]);
        //        (a[6], a[7], a[8]) = sgs(a[1]);
        //        (a[9], a[10], a[11]) = sgs(a[2]);
    }

/*    static public (long a, long b, long c) sgs(long d)
    {
        long a = d * 10 + 3;
        long b = d * 10 + 5;
        long c = d * 10 + 7;

        return (a, b, c);
    }
    */
}