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 Common Lisp (SBCL 1.1.14) (judge verdict: Accepted)

(defun sum-d (k)
  (let ((ans 0))
    (loop while (/= k 0) do (incf ans (rem k 10)) (setf k (floor (/ k 10))))
    ans))

(let ((n (read))
      (flg nil))
  (loop for i from 0 while (>= n (expt 10 i)) do (if (= n (expt 10 i)) (setf flg t)))
  (format t "~A~%" (if flg 10 (sum-d n))))