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: Accepted)

using System;
using System.Globalization;
using System.Threading;
using System.Linq;

public static class ProblemA
{
    #region Common routines

    private static int _currentTokenNumber;

    private static string[] _tokens;

    private static void StartReading()
    {
        _currentTokenNumber = 0;

        Thread.CurrentThread.CurrentCulture = CultureInfo.InvariantCulture;

        _tokens = Console.In.ReadToEnd().Split(new[] { ' ', '\t', '\r', '\n' }, StringSplitOptions.RemoveEmptyEntries);
    }

    private static string NextString()
    {
        return _tokens[_currentTokenNumber++];
    }

    private static int NextInt()
    {
        return int.Parse(NextString());
    }

    private static long NextLong()
    {
        return long.Parse(NextString());
    }

    #endregion

    private static void Main(string[] args)
    {
        StartReading();

        int n = NextInt();
        var result = int.MaxValue;
        for (int a = 1; a < n; a++)
        {

            var newResult = GetSum(a) + GetSum(n - a);
            if (newResult < result) result = newResult;
        }
        Console.WriteLine(result);

    }

    private static int GetSum(int a)
    {
        int result = 0;
        while (a > 0)
        {
            result += a % 10;
            a /= 10;
        }

        return result;
    }
}