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)

#![allow(unused, non_snake_case, dead_code, non_upper_case_globals)]
use {
    proconio::{marker::*, *},
    std::{cmp::*, collections::*, mem::*},
};
macro_rules! chmax {
    ($ base : expr ,$ cmp : expr ) => {
        $base = max($base, $cmp);
    };
}
fn main() {
    input! {
       mut n:i64,
    }

    let mut ans = 0;
    if n < 111 {
        for i in 1..=n {
            chmax!(ans, f(i));
        }
        println!("{}", ans);
        return;
    }
    let mut l = 0;
    let mut ketasu = 0;
    while n > 0 {
        l = n % 10;
        ketasu += 1;
        n /= 10;
    }
    println!("{}", l + 9 * (ketasu - 1) - 1);
}
const INF: i64 = 1 << 60;

fn f(n: i64) -> i64 {
    let mut n = n;
    let mut ans = 0;
    while n > 0 {
        ans += n % 10;
        n /= 10;
    }
    return ans;
}