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: Runtime Error)

def dsum(n)
  m = n.dup
  ret = 0
  while m > 0
    ret += m % 10
    m /= 10
  end
  ret
end

n = gets.to_i
ans = Float::INFINITY
for a in 1...n do
  b = n - a
  ans = [dsum(a) + dsum(b), ans].min
end
p ans