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 {
  public static void main(String[] args) {
    Scanner scn = new Scanner(System.in);
    int N = scn.nextInt();
    int digit = String.valueOf(N).length();

    ArrayList<Integer> combis = new ArrayList<>();
    for (int i = digit; i >= 3; i--) {
      calcCombi("", i, combis);
    }
    ArrayList<Integer> validCombis = new ArrayList<>();
    for (int combi : combis) {
      if (combi <= N) {
        validCombis.add(combi);
      }
    }

    System.out.println(validCombis.size());

  }

  public static void calcCombi(String str, int D, ArrayList<Integer> combis) {
    if (D == 0) {
      boolean exists3 = false;
      boolean exists5 = false;
      boolean exists7 = false;
      for (char digit : str.toCharArray()) {
        switch (digit) {
        case '3':
          exists3 = true;
          break;
        case '5':
          exists5 = true;
          break;
        case '7':
          exists7 = true;
          break;
        }

        if (exists3 && exists5 && exists7) {
          combis.add(Integer.parseInt(str));
          break;
        }
      }
    } else {
      calcCombi(str + '3', D - 1, combis);
      calcCombi(str + '5', D - 1, combis);
      calcCombi(str + '7', D - 1, combis);
    }

  }

}