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;

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

fn check357(v: &Vec<usize>) -> bool {
    let mut is3 = false;
    let mut is5 = false;
    let mut is7 = false;

    for i in 0..v.len() {
        if v[i] == 3 {
            is3 = true;
        }
        if v[i] == 5 {
            is5 = true;
        }
        if v[i] == 7 {
            is7 = true;
        }
    }

    return is3 && is5 && is7;
}

fn dfs(ns: String, limit: i64) -> usize {
    let num = ns.parse::<i64>().unwrap();
    let mut sum = 0;

    if num <= limit && ns.contains("3") && ns.contains("5") && ns.contains("7") {
        sum += 1;
    }

    if num > limit {
        return 0;
    }

    sum += dfs(ns.clone() + "3", limit);
    sum += dfs(ns.clone() + "5", limit);
    sum += dfs(ns.clone() + "7", limit);
    sum
}

fn main() {
    let n = read();
    let mut sum = 0;

    sum += dfs(String::from("3"), n);
    sum += dfs(String::from("5"), n);
    sum += dfs(String::from("7"), n);

    println!("{}", sum);
}