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# (.NET Core 3.1.201) (judge verdict: Accepted)

using System;

namespace ProgramingStydying
{
    class Program
    {
        static void Main(string[] args)
        {
            var n = int.Parse(Console.ReadLine());
            var ans = 100;

            for(int i = 1; i < n; i++)
            {
                var a = i;
                var b = n - i;
                var sum = ScaleSum(a) + ScaleSum(b);
                
                if(sum < ans)
                {
                    ans = sum;
                }
            }
            Console.WriteLine(ans);
        }

        public static int ScaleSum(int x)
        {
            var sum = 0;

            while(x > 0)
            {
                sum += x % 10;
                x /= 10;
            }
            return sum;
        }
    }
}