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::Read;

pub fn read_stdin() -> String {
    let mut s = String::new();
    ::std::io::stdin().read_to_string(&mut s).unwrap();
    s
}

pub trait Parse {
    fn to<T>(&mut self) -> T
    where
        T: std::str::FromStr;
}

impl<'a> Parse for std::str::SplitWhitespace<'a> {
    fn to<T>(&mut self) -> T
    where
        T: std::str::FromStr,
    {
        let word = self.next().unwrap();
        word.parse().ok().unwrap()
    }
}

fn vec_357(x: u32, start: u32, end: u32, out: &mut Vec<u32>) {
    for i in vec![3, 5, 7] {
        let xx = x + i * start;
        out.push(xx);
        if start < end {
            vec_357(xx, start * 10, end, out);
        }
    }
}

fn is_357(mut x: u32) -> bool {
    let mut v = Vec::new();
    while x > 0 {
        v.push(x % 10);
        x /= 10;
    }
    v.sort();
    v.dedup();
    v.len() == 3
}

fn main() {
    let source = read_stdin();
    let mut iter = source.split_whitespace();
    let n = iter.to();
    let mut v: Vec<u32> = Vec::new();
    vec_357(0, 1, 10_u32.pow(8), &mut v);
    println!("{}", v.into_iter().filter(|&x| x <= n && is_357(x)).count());
}