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.Collections.Generic;

namespace ConsoleApp1
{
	class Program
	{
		static void Main(string[] args)
		{
			string input = Console.ReadLine();
			int num = int.Parse(input);
			if (num < 357)
			{
				Console.WriteLine(0);
				return;
			}
			List<string> data = new List<string>() { "357", "375", "537", "573", "735", "753" };

			for(int i = 3; i < input.Length; i++)
			{
				List<string> temp = new List<string>();
				temp.AddRange(data);
				foreach (var v in data)
				{
					temp.AddRange(push(v));
				}
				data.Clear();
				data.AddRange(temp);
				data = data.Distinct().ToList();
			}
			var result = data.Where(x => int.Parse(x) <= num);

			Console.WriteLine(result.Count());
		}
		static string[] push(string input)
		{
			List<string> data = new List<string>();
			for (int i = 0; i < input.Length + 1; i++)
			{
				data.Add(input.Insert(i, "3"));
			}
			for (int i = 0; i < input.Length + 1; i++)
			{
				data.Add(input.Insert(i, "5"));
			}
			for (int i = 0; i < input.Length + 1; i++)
			{
				data.Add(input.Insert(i, "7"));
			}
			return data.Distinct().ToArray();
		}
	}
}