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.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.Arrays;
import java.util.StringTokenizer;

public class Main {

  public static void main(String[] args) {
    InputReader in = new InputReader(System.in);
    PrintWriter out = new PrintWriter(System.out);

    int n = in.nextInt();

    out.println(shichiGoSan(n, ""));

    out.close();
  }

  static int shichiGoSan(int n, String s) {
    if (s.length() > 9)
      return 0;

    boolean seven = false, five = false, three = false;

    for (int i = 0; i < s.length(); i++) {
      if (s.charAt(i) == '7')
        seven = true;
      if (s.charAt(i) == '5')
        five = true;
      if (s.charAt(i) == '3')
        three = true;
    }

    int ret = (seven && five && three) ? 1 : 0;

    if (s.length() == 0 || Integer.parseInt(s) <= n) {
      return ret
          + shichiGoSan(n, s + '3')
          + shichiGoSan(n, s + '5')
          + shichiGoSan(n, s + '7');
    }

    return 0;
  }

  static class InputReader {
    public BufferedReader reader;
    public StringTokenizer tokenizer;

    public InputReader(InputStream stream) {
      reader = new BufferedReader(new InputStreamReader(stream), 32768);
      tokenizer = null;
    }

    public String next() {
      while (tokenizer == null || !tokenizer.hasMoreTokens()) {
        try {
          tokenizer = new StringTokenizer(reader.readLine());
        } catch (IOException e) {
          throw new RuntimeException(e);
        }
      }
      return tokenizer.nextToken();
    }

    public int nextInt() {
      return Integer.parseInt(next());
    }

    public long nextLong() {
      return Long.parseLong(next());
    }

    public double nextDouble() {
      return Double.parseDouble(next());
    }
  }

  static void print(int[] arr) {
    Arrays.stream(arr).forEach(i -> System.out.print(i + " "));
    System.out.println();
  }

  public static int[] mergeSort(int[] a) {
    if (a.length <= 1)
      return a;

    int mid = a.length / 2;
    int[] left = new int[mid];
    int[] right = new int[a.length - mid];

    for (int i = 0; i < mid; ++i)
      left[i] = a[i];

    for (int i = mid; i < a.length; ++i)
      right[i - mid] = a[i];

    return merge(mergeSort(left), mergeSort(right));
  }

  public static int[] merge (int[] l, int[] r) {
    int[] merged = new int[l.length + r.length];

    int i = 0, j = 0, k = 0;
    while (i < l.length && j < r.length) {
      if (l[i] <= r[j])
        merged[k++] = l[i++];
      else
        merged[k++] = r[j++];
    }

    while (i < l.length)
      merged[k++] = l[i++];
    while (j < r.length)
      merged[k++] = r[j++];

    return merged;
  }

}