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# (.NET Core 3.1.201) (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.Linq;
using static System.Math;

namespace ConsoleApp15
{
    class Class402
    {
        static int[] num = new int[3] { 7, 5, 3 };
        static long N;
        static void Main()
        {
            N = long.Parse(Console.ReadLine());
            int ans = DFS(0, 0,false,false,false);
            Console.WriteLine(ans);
        }
        static int DFS(long value, int leng,bool f7,bool f5,bool f3)
        {
            int ans = 0;
            if (f7 && f5 && f3) ans++;
            for(int i = 0; i < 3; i++)
            {
                long n = value + num[i]*(long)Pow(10,leng);
                if (n > N) continue;
                if (i == 0)
                {
                    ans += DFS(n, leng + 1, true, f5, f3);
                }
                if (i == 1)
                {
                    ans += DFS(n, leng + 1, f7, true, f3);
                }
                if (i == 2)
                {
                    ans += DFS(n, leng + 1, f7, f5, true);
                }
            }
            return ans;
        }
    }
}