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 PHP (7.4.4) (judge verdict: Accepted)

<?php
list($s) = strs();
echo max(((int) $s[0] - 1) + (strlen($s) - 1) * 9, digitSum($s));
function strs()
{
    return explode(' ', trim(fgets(STDIN)));
}
function digitSum($n)
{
    return array_sum(array_map('intval', str_split((string) $n)));
}