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

namespace AtCoder {
    public class Program {
        static void Main() {
            int N = int.Parse(Console.ReadLine());
            int L = N.ToString().Length;
            char[] numbers = new char[] { '3', '5', '7' };
            List<string> Answers = new List<string>();
            Queue<string> Keys = new Queue<string>();
            Keys.Enqueue("");
            for (int i = 0; i < L; i++) {
                Queue<string> next = new Queue<string>();
                foreach (var k in Keys) {
                    foreach (var c in numbers) {
                        string k_app = k + c.ToString();
                        if (k_app.Contains('3') && k_app.Contains('5') && k_app.Contains('7')) Answers.Add(k_app);
                        next.Enqueue(k_app);
                    }
                }
                Keys = next;
            }

            Console.WriteLine(Answers.Where(x => int.Parse(x)<=N).Count());
        }
    }
}