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.*;
import java.io.*;

public class Main {
	private static void solve(){
		//Implement solution here.
		int n = ni();
		int len = Integer.toString(n).length();
		int result = 0;
		
		result = dfs(1, 3, n) + dfs(1, 5, n) + dfs(1, 7, n);
		
		System.out.println(result);
	}
	
	private static int dfs(int dig, int cur, int max) {
		int result = 0;	
		if(dig >= 3) {
			if(dig <= Integer.toString(max).length()) {
				if(cur <= max) {
					if(is753(cur))result++;
				} else {
					return 0;
				}
			} else {
				return 0;
			}
		}	
		dig++;
		result += dfs(dig, cur * 10 + 3, max) + dfs(dig, cur * 10 + 5, max) + dfs(dig, cur * 10 + 7, max);
		return result;
	}

	private static boolean is753(int in) {
		boolean[] flags = new boolean[3];
		char[] inca = Integer.toString(in).toCharArray();
		for(char c:inca) {
			if(c == '3')flags[0] = true;
			if(c == '5')flags[1] = true;
			if(c == '7')flags[2] = true;
		}
		
		return flags[0] && flags[1] && flags[2];
	}
	//Switch input source (stdin/file)
	private static Scanner scanner = new Scanner(System.in);
	public static void main(String[] args){
		String debugDataPath = System.getenv("DD_PATH");        
		if(debugDataPath != null){
			try{
				scanner = new Scanner(new BufferedReader(new InputStreamReader(new FileInputStream(new File(debugDataPath)))));
			}catch(Exception e){
				throw new RuntimeException(e);
			}
		}
		solve();
	}

	//Input read utility
	private static StringTokenizer tokenizer = null;
	public static String next() {
		while (tokenizer == null || !tokenizer.hasMoreTokens()) {
			try {
				tokenizer = new StringTokenizer(scanner.nextLine());
			} catch (Exception e) {
				throw new RuntimeException(e);
			}
		}
		return tokenizer.nextToken();
	}
	//Get next single int
	private static int ni() {
		return Integer.parseInt(next());
	}
	//Get next single long
	private static long nl() {
		return Long.parseLong(next());
	}
	//Get next single double
	private static double nd() {
		return Double.parseDouble(next());
	}
	//Get next int array from one line
	private static int[] na(int n) {
		int[] a = new int[n];
		for (int i = 0; i < n; i++)
			a[i] = ni();
		return a;
	}
	//Get next char array from one line
	private static char[] ns() {
		return next().toCharArray();
	}
	//Get next long array from one line
	private static long[] nal(int n) {
		long[] a = new long[n];
		for (int i = 0; i < n; i++)
			a[i] = nl();
		return a;
	}
}