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

namespace TestApp2
{
    class Program
    {
        static void Main(string[] args)
        {
            var num = int.Parse(Console.ReadLine());
            var vv = num / 2;
            var xx = int.MaxValue;
            for (int i = 1; i <= vv+1; i++)
            {
                var st1 = i.ToString().Sum(x => int.Parse(x.ToString()));
                var st2 = (num - i).ToString().Sum(x => int.Parse(x.ToString()));
                var ss = st1 + st2;
                if (ss < xx)
                    xx = ss;
            }
            Console.WriteLine(xx);
            Console.ReadLine();
        }


    }
}