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;
using System.Collections;
using System.Collections.Generic;
using System.Text;


public class A
{
	public static void Main()
	{		
		int N = Int32.Parse(Console.ReadLine());

		int ans = Int32.MaxValue;
		for(int A = 1; A <= N - 1; A++)
		{
			int B = N - A;
			ans = Math.Min(ans, digitsSum(A) + digitsSum(B));
		}

		Console.WriteLine(ans);
	}

	public static int digitsSum(int x)
	{
		int tmp = x;
		int ans = 0;
		while(tmp > 0)
		{
			ans += tmp % 10;
			tmp /= 10;
		}

		return ans;
	}
}