Problem:
Score : 300 points

Problem Statement

Find the maximum possible sum of the digits (in base 10) of a positive integer not greater than N.

Constraints

1\leq N \leq 10^{16}

N is an integer.

Input

Input is given from Standard Input in the following format:

N

Output

Print the maximum possible sum of the digits (in base 10) of a positive integer not greater than N.

Sample Input 1

100

Sample Output 1

18

For example, the sum of the digits in 99 is 18, which turns out to be the maximum value.

Sample Input 2

9995

Sample Output 2

35

For example, the sum of the digits in 9989 is 35, which turns out to be the maximum value.

Sample Input 3

3141592653589793

Sample Output 3

137

Solution in Rust (1.15.1) (judge verdict: Wrong Answer)

use std::{io};


fn main() {
    let mut input = String::new();
    match io::stdin().read_line(&mut input) {
        Ok(n) => {
            let f = (input.as_bytes()[0] - 0x30) as usize;
            println!("{}", f-1 + 9*(n-2));
        }
        Err(_) => {}
    }
}