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_a
{
    class Program
    {
        static void Main(string[] args)
        {
            int n = int.Parse(Console.ReadLine());
            long ret = long.MaxValue;
            for (int i = 0; i < n; i++)
            {
                int a = i; int b = n - i;
                if (Math.Min(a, b) <= 0) continue;
                string c = a.ToString(); string d = b.ToString();
                int now = 0;
                for (int j = 0; j < c.Length; j++) now += int.Parse(c[j].ToString());
                for (int j = 0; j < d.Length; j++) now += int.Parse(d[j].ToString());
                ret = Math.Min(ret, now);
            }
            Console.WriteLine(ret);
        }
    }
}