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;
public class Hello{
    static int Sum(int n){
        int ans = 0;
        while(n > 0){
            ans += n % 10;
            n /= 10;
        }
        
        return ans;
    }
    public static void Main(){
        int n = int.Parse(Console.ReadLine());
        int ans = int.MaxValue;
        for(var i = 1;i < n;i++){
            int j = n - i;
            ans = Math.Min(ans,Sum(i) + Sum(j));
        }
        Console.WriteLine(ans);
    }
}