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 Lua (5.3.2) (judge verdict: Accepted)

local n = io.read("*n")
local hn = n // 2

local function get(x)
  local r = 0
  while 0 < x do
    r = r + x % 10
    x = x // 10
  end
  return r
end
local mmi = math.min
local ret = get(1) + get(n - 1)
for i = 2, hn do
  ret = mmi(ret, get(i) + get(n - i))
end
print(ret)