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)

#![allow(non_snake_case)]

fn read_line() -> String {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).unwrap();
    s.trim().to_string()
}

fn to_base3(n: i32) -> String {
    let q = n / 3;
    let r = n % 3;
    if q == 0 {
        r.to_string()
    } else {
        to_base3(q) + &r.to_string()
    }
}

fn main() {
    let N: u32 = read_line().parse().unwrap();
    let len = N.to_string().len();
    if len < 3 {
        println!("0");
        return;
    }
    let mut ans: i32 = (2..len as u32).map(|x| 3_i32.pow(x) - 3*2_i32.pow(x) + 3).sum();
    for n in 0..3_i32.pow(len as u32) {
        let mut s: Vec<char> = to_base3(n).chars().collect();
        while s.len() < len {
            s.insert(0, '0');
        }
        if N < s.iter().fold(0, |sum, &d| sum*10 +  d.to_digit(10).unwrap()*2+3) {
            break;
        }
        if s.contains(&'0') && s.contains(&'1') && s.contains(&'2') {
            ans += 1;
        }
    }
    println!("{}", ans);
}