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 C# (Mono 4.6.2.0) (judge verdict: Wrong Answer)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace atcoder
{
    class Program
    {
        static void Main(string[] args)
        {
            int N = int.Parse(Console.ReadLine());
            int answer = digits(N, N.ToString().Length);
            int digit = 0;
            for(int i = 1; i < N; i++)
            {
                digit = 0;
                digit += digits(i, i.ToString().Length) + digits(N, (N - i).ToString().Length);
                if (answer >= digit) answer = digit;
            }
            Console.WriteLine(answer);
        }

        static int digits(int C, int len)
        {
            int digit_sum = 0;
            for (int i = 0; i < len; i++)
            {
                digit_sum += C % 10;
                C = C / 10;
            }
            return digit_sum;
        }
    }
}