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 (
	"bufio"
	"fmt"
	"os"
	"strconv"
	"strings"
)

var n int
var count = 0
var numsOf753 = [3]string{"3", "5", "7"}

func dfs(v string) {
	if strings.Contains(v, "3") && strings.Contains(v, "5") && strings.Contains(v, "7") {
		count++
	}

	for _, next := range numsOf753 {
		tmp := next + v
		if m, _ := strconv.Atoi(tmp); m > n {
			continue
		}

		dfs(tmp)
	}
}

func main() {
	n = getInt()

	for _, v := range numsOf753 {
		dfs(v)
	}

	fmt.Println(count)
}

// -----------------------------------------

var sc = bufio.NewScanner(os.Stdin)

func init() {
	// tmp := 200001
	// sc.Buffer(make([]byte, tmp), tmp)
	sc.Split(bufio.ScanWords)
}

func getInt() int {
	i, err := strconv.Atoi(getString())
	if err != nil {
		panic(err)
	}
	return i
}

func getString() string {
	sc.Scan()
	s := sc.Text()
	return s
}