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 (1.42.0) (judge verdict: Wrong Answer)

use proconio::{fastout, input};
use std::collections::BTreeMap;

#[fastout]
fn main() {
    input! {n: u128};
    let n: u128 = n;

    let n1 = &n.to_string()[0..1];

    if n1 == "1" {
        println!("{}", (n.to_string().len() - 1) * 9)
    } else if n1 == "9" {
    } else {
        let x: usize = n1.parse().unwrap();
        println!("{}", ((n.to_string().len() - 1) * 9) + x - 1);
    }
}