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.Collections.Generic;
using System.Linq;
class Program{
	static int[] h;
	static int ans=0,l=0,n;
	static void Main(){
		string s=Console.ReadLine();
		n=int.Parse(s);
		l=s.Length;
		h=new int[l];
		fu(0,1,0);
		Console.WriteLine(ans);
	}
	static void fu(int a,int b,int c){
		if(a==l){
			if(c==7&&n>=int.Parse(String.Join("",h))){ans++;}
		}
		else{
			h[a]=3;fu(a+1,0,c|1);
			h[a]=5;fu(a+1,0,c|2);
			h[a]=7;fu(a+1,0,c|4);
			if(b==1){h[a]=0;fu(a+1,1,c);}
		}
	}
}