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 (2.7.1) (judge verdict: Accepted)

n = gets.chomp.to_i

result = 0

(1..(n-1)).each do |i|
  i2 = ("%#05d" % i).chars.map(&:to_i)
  j = ("%#05d" % (n - i)).chars.map(&:to_i)
  i_sum = 0
  j_sum = 0
  (0..4).each{|k| i_sum += i2[k]; j_sum += j[k] }
  sum = i_sum + j_sum
  if result == 0 || sum < result
    result = sum
  end
end

print result