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: Wrong Answer)

<?php /*atcoder.php*/

$t = new temp();

$t->stdin(fgets(STDIN));

unset($t);

class temp{
	public function stdin($data = null){
		$max = $data;
		$s = array_reverse(str_split($data));
		$di = count($s);

		if(1 == $di){
			echo $max;
		}

		for($i = 0; $i < $di; $i++){
			if(9 != $s[$i]){
				if(array_key_exists(($i + 1) ,$s)){
					$s[$i] = 9;
					$s[($i + 1)]--;
				}
			}
		}
		$ans = 0;
		for($i = 0; $i < $di; $i++){
			$ans += $s[$i];
		}

		echo $ans;
		
	}
	
}

?>