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;

namespace AGC025
{
    class Program
    {
        static void Main(string[] args)
        {
            int N = int.Parse(Console.ReadLine());

            int min = int.MaxValue;
            int sum = 0;
            int nA = 0;
            int nB = 0;

            for (int i = 1; i < N; i++)
            {
                nA = i;
                nB = N - i;
                while (0 < nA)
                {
                    sum += nA % 10;
                    nA = nA / 10;
                }

                while (0 < nB)
                {
                    sum += nB % 10;
                    nB = nB / 10;
                }

                min = Math.Min(min, sum);
                sum = 0;

            }

            Console.WriteLine(min);
        }
    }
}