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: Wrong Answer)

<?php

  $N = trim(fgets(STDIN));


  if(!is_int($N)){
    return;
  }

  if($N < 2 || 100000 < $N){
    return;
  }

  for($j = 1; $j < $N; $j++){

    $a[] = getSumOfEachLevel($j);

  }

  $b = array_reverse($a);

  for($j = 1; $j < $N; $j++){

    $c[] = $a[$j] + $b[$j];

  }

  return min($c);


  function getSumOfEachLevel($value){

    $result    = 0;
    $usedValue = $value;
    $i = 10;

    while($i < $value){

      // 対象桁の数字
      $levelValue = ($usedValue % $i) / ($i /10);
      // 求めたい和
      $result += $levelValue;
      // 元の値から対象桁の数字を引いていく
      $usedValue -= $levelValue * ($i/10);

      $i * 10;

    }

  }