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 OCaml (4.02.3) (judge verdict: Accepted)

let rec digits_sum = function
  | 0 -> 0
  | n -> n mod 10 + digits_sum (n / 10)

let () = Scanf.scanf "%d" @@ fun n ->
  Array.init (n - 1) (fun a -> a + 1, n - a - 1)
  |> Array.map (fun (a, b) -> digits_sum a + digits_sum b)
  |> Array.fold_left min max_int
  |> Printf.printf "%d\n"