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 Rust (1.15.1) (judge verdict: Accepted)

use std::io::*;
use std::str::FromStr;

fn func(n: i64, mut now: i64) -> i64 {
    if n < now {
        return 0;
    }
    now *= 10;
    let mut ans = 0;
    if check753(now) {
        ans += 1;
    }
    ans += func(n, now + 7);
    ans += func(n, now + 5);
    ans += func(n, now + 3);
    return ans;
}

fn check753(mut n: i64) -> bool {
    let mut ok = [false, false, false];
    while n > 0 {
        match n % 10 {
            3 => ok[0] = true,
            5 => ok[1] = true,
            7 => ok[2] = true,
            _ => {}
        }
        n /= 10;
    }
    return ok[0] && ok[1] && ok[2];
}

fn main() {
    let n: i64 = read();
    println!("{}", func(n, 0));
}

fn read<T: FromStr>() -> T {
    let stdin = stdin();
    let stdin = stdin.lock();
    let token: String = stdin
        .bytes()
        .map(|c| c.unwrap() as char)
        .skip_while(|c| c.is_whitespace())
        .take_while(|c| !c.is_whitespace())
        .collect();
    token.parse().ok().unwrap()
}