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: Wrong Answer)

import Control.Applicative
import Control.Monad
import qualified Data.List
import qualified Data.Char as C
import Debug.Trace

main ::IO()
main = do
  n <- read <$> getLine -- :: IO Int
  putStrLn $ show $ solve n 

solve :: Int -> Int 
solve n =
  ans
  where
    m = ceiling $ fromIntegral n / 10
    n' = n-m
    cand1 =digs m+ digs n'
    cand2 = digs n
    ans = maximum [cand1,cand2]

-- -- functions --

digs :: Integral x => x -> x
digs 0 = 0
digs x = x `mod` 10 + digs (x `div` 10)