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)

def f(x)
   [10,100,1000,10000,100000,1000000].map{|k|
    x%k/(k/10)
  }.inject(:+)
end
n=gets.to_i
p n.times.map{|m|
  a=f(n-m)
  b=f(m)
  if (a < 1 || b < 1)
    a * 10 + b * 10
  else
    a + b
  end
}.min