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 main() {
    use std::io::Read;
    let mut buf = String::new();
    std::io::stdin().read_to_string(&mut buf).unwrap();
    let mut iter = buf.split_whitespace();
    
    let n: u64 = iter.next().unwrap().parse().unwrap();
    let mut nums = vec![];
    dfs(0, n, &mut nums);


    println!("{}",
        nums.into_iter()
        .filter(|&i| sft_only(i))
        .count()
    );
}

fn dfs(k: u64, n: u64, acc: &mut Vec<u64>) {
    if k > n {
        return;
    }
    acc.push(k);
    dfs(k * 10 + 7, n, acc);
    dfs(k * 10 + 5, n, acc);
    dfs(k * 10 + 3, n, acc);
}

fn sft_only(mut k: u64) -> bool {
    let mut hmap = std::collections::HashMap::new();
    while k != 0 {
        *hmap.entry(k%10).or_insert(0) += 1;
        k /= 10;
    }
    *hmap.get(&7).unwrap_or(&0) >= 1 &&
    *hmap.get(&5).unwrap_or(&0) >= 1 &&
    *hmap.get(&3).unwrap_or(&0) >= 1 &&
    *hmap.get(&0).unwrap_or(&0) == 0
}