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

namespace AtCoder
{
    class Program
    {
        static void Main(string[] args)
        {
            var N = int.Parse(Console.ReadLine());
            var result = 1000000000;
            for (var i=1; i<=N/2; i++)
            {
                var a = i;
                var b = N - i;
                var digitsSumA = a.ToString().ToCharArray().Select(x => int.Parse(Convert.ToString(x))).Sum();
                var digitsSumB = b.ToString().ToCharArray().Select(x => int.Parse(Convert.ToString(x))).Sum();

                if (digitsSumA + digitsSumB < result) result = digitsSumA + digitsSumB;
            }

            Console.WriteLine(result);
        }
    }

}