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 Ruby (2.3.3) (judge verdict: Accepted)

n = gets.to_i

ret = 0
(1..n).each do |a|
  b = n - a
  break if a > b

  sum = a.to_s.split('').map(&:to_i).inject(:+)
  sum += (n - a).to_s.split('').map(&:to_i).inject(:+)
  ret = sum if sum < ret || ret < 1
end
puts ret