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 (5.6.30) (judge verdict: Accepted)

<?php
fscanf(STDIN, "%d", $a);

$ary = str_split($a);

for ($i = count($ary)-1; $i >= 1; $i--) {
    if (isset($ary[$i-1]) && $ary[$i] != 9) {
        $ary[$i] = 9;
        $ary[$i-1]--;
    }
}

$total = 0;
foreach ($ary as $v) {
    $total += $v;
}

echo $total;