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 `div` 2)]]

sod
  :: Int -> Int
sod n
  | n `elem` [10^p | p <- [1..5]] = 10 -- 100 = 50+50 case 
  | otherwise = sum $ sod' n

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

sod2 :: Int -> Int -> Int
sod2 x y = sod x + sod y

g :: Int -> Int
g = minimum . map (uncurry sod2) . f