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;

public class AtCoder
{
    public static void Main()
    {
        long n;
        n = int.Parse(Console.ReadLine().Trim());
        int ans = 0;
        int[] j = new int[3];
        for (int i = 1; i <= 10; i++)
        {
            ans += test.F357(n, i, 0, 0, 0, j);
        }
        Console.WriteLine(ans);
    }


}

public class test
{
    public static int F357(long n, int m, int c, long d, int a, int[] j)
    {
        if (c == m)
        {
            if (j[0] * j[1] * j[2] == 0) return a;
            if (d <= n)
            {
                a++;
                //Console.WriteLine(j[0]+" "+j[1]+" "+j[2]);
            }
            return a;
        }
        long p = (long)Math.Pow(10, c);
        c++;
        d += p * 3;
        j[0]++;
        a=F357(n, m, c, d, a, j);
        d += p * 2;
        j[0]--; j[1]++;
        a=F357(n, m, c, d, a, j);
        d += p * 2;
        j[1]--; j[2]++;
        a=F357(n, m, c, d, a, j);
        j[2]--;
        return a;
    }
}