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 sc = new Scanner(System.in);
      int N = sc.nextInt();
      int[] arr = new int[] {3, 5, 7};

      System.out.println(dfs(0, arr, N));
  }

  private static int dfs(long curNum, int[] arr, int N) {
    if(curNum > N)
      return 0;

    int res = check(curNum, arr) ? 1 : 0;
    for(int a : arr) {
      res += dfs(curNum * 10 + a, arr, N);
    }
    return res;
  }

  private static boolean check(long curNum, int[] arr) {
    boolean[] flags = new boolean[10];
    while(curNum > 0) {
      flags[(int)(curNum % 10)] = true;
      curNum /= 10;
    }
    return flags[3] && flags[5] && flags[7];
  }
}