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.Generic;
using static System.Console;

class Program {
    static void Main() {
        var n = NextInt();
        var ans = int.MaxValue;

        for (var a = 1; a < n; a++) {
            var b = n - a;
            ans = Math.Min(ans, DigitsSum(a) + DigitsSum(b));
        }
        WriteLine(ans);
    }

    static int DigitsSum(int x) {
        var result = 0;
        while (x != 0) {
            result += x % 10;
            x /= 10;
        }
        return result;
    }

    static int NextInt() {
        return int.Parse(NextString());
    }

    static string NextString() {
        var result = new List<char>();
        while (true) {
            int next = Read();
            if (next < 0)
                break;
            var nextChar = (char)next;
            if (!char.IsWhiteSpace(nextChar))
                result.Add(nextChar);
            else if (nextChar != '\r')
                break;
        }
        return string.Join("", result);
    }
}