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: Wrong Answer)

N=gets.to_i
a = 1
b = 0
l = []
while a < (N / 2) && b < N do
  b = N - a
  m = 0
  n = (a.to_s + b.to_s).split""
  n.each do |k|
    m += k.to_i
  end
  l << m
  a += 1
end
puts l.min