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 AGC025A
{
    class Program
    {
        static void Main(string[] args)
        {
            int N = int.Parse(Console.ReadLine());
            int min = 1000000;
            for(int a = 1; a < N; a++){
                int b = N-a;
                int wa_tmp =  wa(a) + wa(b);
                if(wa_tmp < min ) min = wa_tmp;
            }
            Console.WriteLine(min);
        }
        public static int wa(int x){
            int ans = 0;
            while(x > 0){
                ans += x % 10; x /= 10;
            }            
            return ans;
        }
    }
}