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 Go (1.6) (judge verdict: Accepted)

package main

import (
	"fmt"
	"regexp"
)

var pattern = regexp.MustCompile("((3+5+7+)|(3+7+5+)|(5+3+7+)|(5+7+3+)|(7+5+3+)|(7+3+5+))+")

func main() {
	var n int
	fmt.Scan(&n)
	fmt.Println(dfs(n, 0))
}

func dfs(max, data int) int {
	if data > max {
		return 0
	}
	var result int
	if pattern.MatchString(fmt.Sprint(data)) {
		result += 1
	}
	return dfs(max, data*10+3) + dfs(max, data*10+5) + dfs(max, data*10+7) + result
}