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)

# Your code here!

def digitsum(v)
    s=0
    while v>0
        s += v%10
        v /= 10
    end
    return s
end

N=gets.to_i
minsum=1000000000
(1..N-1).each{|a|
    b = N - a
    s = digitsum(a)+digitsum(b)
        # puts "a=#{a}, b=#{b}, s=#{s}, minsum=#{minsum}"
    minsum = [minsum, s].min
}
puts minsum