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 Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.util.*;
public class Main {
    static int count = 0;
    static int[] nums = {3, 5, 7};
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        helper(n, "3", 1, 0, 0);
        helper(n, "5", 0, 1, 0);
        helper(n, "7", 0, 0, 1);
        System.out.println(count);
    }
    private static void helper(int n, String strNum, int three, int five, int seven) {
        long num = Long.parseLong(strNum);
        if(num > n) return;
        if(three >= 1 && five >= 1 && seven >= 1) count++;
        helper(n, strNum + "3", three + 1, five, seven);
        helper(n, strNum + "5", three, five + 1, seven);
        helper(n, strNum + "7", three, five, seven + 1);
    }
}