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)

num = gets.chomp.to_i
N = num.to_s.split("").map { |e| e.to_i }

flag = 0
for i in 1..N.length-1 do
  if N[i] != 0
    flag = 1
  elsif flag == 1
    break
  end
end

if flag == 1 #キリがいい数字じゃない
  count = 0
  for i in 0..N.length-1 do
    count += N[i]
  end
elsif N.length-1 == 2
  count = num
elsif N[0] == 1
  count = N[0]*10
else
  count = N[0]
end

puts count