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)


fn func(input_str: &str) -> u32 {
    let mut iter = input_str.split_whitespace();
    let n: usize = iter.next().unwrap().parse().unwrap();
    let m: usize = (n as f64).log10() as usize + 1;
    let mut cand = vec![vec![String::new()]; 10];
    let c_s = ["3", "5", "7"];
    let mut ans = 0;
    for i in 1..m+1 {
        let mut buf = Vec::new();
        for s in cand[i - 1].iter() {
            for &c in &c_s[..] {
                let ns = s.clone() + c;
                let x: usize = ns.parse().unwrap();
                if c_s.iter().all(|c| ns.contains(c)) 
                    && x <= n {
                    ans += 1;
                }
                buf.push(ns);
            }
        }
        cand[i] = buf;
    }
    ans
}

use std::io::Read;

fn main() {
    let mut buf = String::new();
    std::io::stdin().read_to_string(&mut buf).unwrap();
    println!("{}", func(&buf[..]));
}