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
a = 1
b = 0
answers = []
while a < N && b < N && b >= 0 do
  b = N - a
  ax = a.to_s.split""
  bx = b.to_s.split""
  sumA = 0
  sumB = 0
  ax.each do |k|
    sumA += k.to_i
  end
  bx.each do |k|
    sumB += k.to_i
  end
  answers << sumA + sumB
  a += 1
end
puts answers.min