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, stdin};
use std::str::FromStr;

fn main() {
    let n: i64 = read();
    let mut v: Vec<i64> = Vec::new();
    v = dfs(0, v, n);
    println!("{}", v.len())
}

fn dfs(x: i64, mut v: Vec<i64>, n: i64) -> Vec<i64>{
    if x <= n{
        if 0 < x && is_357(x){
            v.push(x);
        }
        v = dfs(x*10 + 3, v, n);
        v = dfs(x*10 + 5, v, n);
        v = dfs(x*10 + 7, v, n);
    }
    v
}

fn is_357(x: i64) -> bool {
    let s : String = x.to_string();
    let mut is3:bool = false;
    let mut is5:bool = false;
    let mut is7:bool = false;
    for c in s.chars(){
        if c == '3'{
            is3 = true;
        }
        if c == '5'{
            is5 = true;
        }
        if c == '7'{
            is7 = true;
        }
    }
    is3 && is5 && is7
}

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")
}