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 Sample101
{
    class Program
    {
        // 各桁の和を計算
        static int findSumOfDigits(int n)
        {
            int sum = 0;
            while (n > 0)
            {
                sum += n % 10;
                n /= 10;
            }
            return sum;
        }

        static void Main(string[] args)
        {
            int N = int.Parse(Console.ReadLine());
            int result;

            result = 1 + findSumOfDigits(N - 1);

            for (int i = 2; i < N / 2; ++i)
            {
                int A = i;
                int B = N - i;
                int temp = findSumOfDigits(A) + findSumOfDigits(B);
                if (temp < result)
                {
                    result = temp;
                }
            }

            Console.WriteLine(result);
        }
    }
}