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 dfs(s: &str, N: u32) -> i32 {
    if s.parse::<u64>().unwrap() > N as u64 {
        0
    } else {
        let digits = ['3', '5', '7'];
        let mut ret = if digits.iter().map(|&x|
            s.chars().collect::<Vec<char>>().iter()
                .filter(|&&c| c == x)
                .count()
        ).collect::<Vec<usize>>().iter().all(|&x| x > 0) {
            1
        } else {
            0
        };
        for &c in digits.iter() {
            ret += dfs(&(s.to_string() + &c.to_string()), N);
        }
        ret
    }
}

fn main() {
    let N: u32 = read_line().parse().unwrap();
    println!("{}", dfs(&"0".to_string(), N));

}