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: Time Limit Exceeded)

import java.util.*;

public class Main {

    public static void main(String[] args) {
        // write your code here
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();

        long ans = 0;

        int max = String.valueOf(n).length();

        StringBuilder sevenBuilder = new StringBuilder();
        // 7の数
        for (int i = 1; i <= max - 2; i++) {
            sevenBuilder.append("7");
            StringBuilder fiveBuilder = new StringBuilder();
             // 5の数
            for (int j = 1; i + j <= max - 1; j++) {
                fiveBuilder.append("5");
                StringBuilder threeBuilder = new StringBuilder();
                // 3の数
                for (int k = 1; i + j + k <= max; k++) {
                    threeBuilder.append("3");
                    permutation(String.valueOf(threeBuilder) + fiveBuilder + sevenBuilder, "");
                    Double[] v = list.toArray(new Double[0]);
                    int index = -(Arrays.binarySearch(v, n + 0.1)) - 1;
                    ans += index;
                    list.clear();
                    if (index != v.length) {
                        break;
                    }
                }
            }
        }

        System.out.println(ans);
    }

    private static TreeSet<Double> list = new TreeSet<>();

    private static void permutation(String q, String ans) {
        // Base Case
        if (q.length() <= 1) {
            list.add(Double.parseDouble(ans + q));
        }
        // General Case
        else {
            for (int i = 0; i < q.length(); i++) {
                permutation(q.substring(0, i) + q.substring(i + 1),
                        ans + q.charAt(i));
            }
        }
    }
}