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)

require 'pp'
# IS_DEBUG = true
IS_DEBUG = false
def dputs str
	if(IS_DEBUG)
		puts str
	end
end
def dpp str
	if(IS_DEBUG)
		pp str
	end
end

MAX_INT = 9999999999999999

N,d=gets.chomp.split(' ').map{|n| n.to_i}

def sum_of_digit(i)
	sum = 0
	tmp = i
	while(tmp > 0)
		sum += tmp % 10
		tmp /= 10
	end
	sum
end
min = MAX_INT
1.upto(N-1){|i|
	j = N - i
	tmp = sum_of_digit(i) + sum_of_digit(j)
	dputs "#{i},#{j}:#{tmp}"
	if(min > tmp)
		min = tmp
	end
}
puts min