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.IO;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;

namespace AtCoder.AGC025
{
    class Program
    {
        static void Main()
        {
            var sc = new Scanner();
            var ns = sc.Next();

            if (string.IsNullOrEmpty(ns.Substring(1)))
            {
                Console.WriteLine(ns);
            }
            else if (int.Parse(ns.Substring(1)) != 0)
            {
                var result = 0;
                foreach (var item in ns)
                {
                    result += int.Parse(item.ToString());
                }
                Console.WriteLine(result);
            }
            else
            {
                var n0 = int.Parse(ns[0].ToString());
                if (n0 == 1)
                {
                    Console.WriteLine(10);
                }
                else
                {
                    Console.WriteLine(n0);
                }
            }
        }
    }
    class Scanner
    {
        string[] s;
        long i;

        char[] cs = new char[] { ' ' };

        public Scanner()
        {
            s = new string[0];
            i = 0;
        }

        public string Next()
        {
            if (i < s.Length) return s[i++];
            string st = Console.ReadLine();
            while (st == "") st = Console.ReadLine();
            s = st.Split(cs, StringSplitOptions.RemoveEmptyEntries);
            if (s.Length == 0) return Next();
            i = 0;
            return s[i++];
        }

        public int Nextint()
        {
            return int.Parse(Next());
        }
        public int[] Arrayint(int N, int add = 0)
        {
            int[] Array = new int[N];
            for (int i = 0; i < N; i++)
            {
                Array[i] = Nextint() + add;
            }
            return Array;
        }

        public long NextLong()
        {
            return long.Parse(Next());
        }

        public long[] ArrayLong(int N, long add = 0)
        {
            long[] Array = new long[N];
            for (long i = 0; i < N; i++)
            {
                Array[i] = NextLong() + add;
            }
            return Array;
        }

        public double NextDouble()
        {
            return double.Parse(Next());
        }

        public double[] ArrayDouble(long N, double add = 0)
        {
            double[] Array = new double[N];
            for (long i = 0; i < N; i++)
            {
                Array[i] = NextDouble() + add;
            }
            return Array;
        }

        public decimal NextDecimal()
        {
            return decimal.Parse(Next());
        }

        public decimal[] ArrayDecimal(long N, decimal add = 0)
        {
            decimal[] Array = new decimal[N];
            for (long i = 0; i < N; i++)
            {
                Array[i] = NextDecimal();
            }
            return Array;
        }
    }
}