Problem:
Score : 200 points

Problem Statement

Takahashi has two positive integers A and B.

It is known that A plus B equals N.
Find the minimum possible value of "the sum of the digits of A" plus "the sum of the digits of B" (in base 10).

Constraints

2 ≤ N ≤ 10^5

N is an integer.

Input

Input is given from Standard Input in the following format:

N

Output

Print the minimum possible value of "the sum of the digits of A" plus "the sum of the digits of B".

Sample Input 1

15

Sample Output 1

6

When A=2 and B=13, the sums of their digits are 2 and 4, which minimizes the value in question.

Sample Input 2

100000

Sample Output 2

10

Solution in PHP (5.6.30) (judge verdict: Runtime Error)

<?php
echo "整数を入力してください\n";
while(1)
{
  $n = fgets(STDIN, 4096);

  if ($n<2 || $n>100000) {
    echo "入力値は、2<=n<=100000で入力してください\n";
    die();
  }

  for ($a=1;$a<$n;$a++)
  {
    $b=$n-$a;
    if (strlen($b)>1)
    {
      for ($i=0; $i<=strlen($b)-1; $i++)
      {
        $sum_b[] = mb_substr($b, $i, 1);
      }
      $sum_b_result = array_sum($sum_b);
      $result[] = $a+$sum_b_result;
    }
    else
    {
      $result[] = $a+$b;
    }
  }
  echo min($result)."\n";
  die();
}