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"
)

func main() {
	fmt.Println(dfs(0, nextInt()))
}

func dfs(x, n int) int {
	if x > n {
		return 0
	}
	ret := 0
	if is753(x) {
		ret = 1
	}
	for i := 3; i <= 7; i += 2 {
		ret += dfs(x*10+i, n)
	}
	return ret
}

func is753(x int) bool {
	m := map[int]int{7: 0, 5: 0, 3: 0}
	for x > 0 {
		m[x%10]++
		x /= 10
	}
	for _, v := range m {
		if v == 0 {
			return false
		}
	}
	return true
}

func lcm(a, b int64) int64 {
	return (a / gcd(a, b)) * b
}

func gcd(a, b int64) int64 {
	for b != 0 {
		a, b = b, a%b
	}
	return a
}

const size = 1000000

var reader = bufio.NewReaderSize(os.Stdin, size)

func nextLine() string {
	var line, buffer []byte
	isPrefix := true
	var err error
	for isPrefix {
		line, isPrefix, err = reader.ReadLine()
		if err != nil {
			panic(err)
		}
		buffer = append(buffer, line...)
	}
	return string(buffer)
}
func nextStringArray() []string {
	return strings.Split(nextLine(), " ")
}
func nextInt() int {
	n, _ := strconv.Atoi(nextLine())
	return n
}

func nextIntArray() []int {
	s := strings.Split(nextLine(), " ")
	n := len(s)
	a := make([]int, n)
	for i := 0; i < n; i++ {
		a[i], _ = strconv.Atoi(s[i])
	}
	return a
}

func min(i, j int) int {
	if i > j {
		return j
	}
	return i
}

func max(i, j int) int {
	if i < j {
		return j
	}
	return i
}