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 floor = math.floor
local min = math.min
local N = io.read("*n")

local function idiv(operand1, operand2)
	return floor(operand1 / operand2)
end

local function sumDigits(num)
	local sum = 0
	while num > 0 do
		sum = sum + num % 10
		num = idiv(num, 10)
	end
	return sum
end

local out = 100001
for A = 1, idiv(N, 2) do
	local B = N - A
	local sum = sumDigits(A) + sumDigits(B)
	out = min(out, sum)
end

print(out)