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.Linq;
using System.Numerics;

    class Program
    {
        static int dfs(string s, BigInteger N)
        {
            if (BigInteger.Parse(s) > N) return 0;
            var ret = 1;
            if (!(s.Contains('7') && s.Contains('5') && s.Contains('3'))) ret = 0;
            foreach (var c in "753")
            {
                ret += dfs(s + c, N);
            }
            return ret;
        }

        static void Main(string[] args)
        {
            var N = BigInteger.Parse(Console.ReadLine());
            Console.WriteLine(dfs("0", N));
        }
    }