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 Haskell (GHC 7.10.3) (judge verdict: Accepted)

main :: IO ()
main = do
  n <- readLn
  print $ g n

f :: Int -> [(Int,Int)]
f n = [(x, n-x) | x <- [1..((n+1) `div` 2)]]

sod :: Int -> Int
sod = sum . sod'
sod' n
  | q == 0 = [r] 
  | otherwise = r : sod' q
  where
    (q,r) = quotRem n 10

g = minimum . map (\(x,y) -> (sod x) + (sod y)) . f