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
result = 10000000
for a in 1..(n-1) do
    aa = 0
    b = n - a
    a.to_s.each_char { |s| aa += s.to_i }
    b.to_s.each_char { |s| aa += s.to_i }
    result = aa if aa < result 
end
print result