Crooked Digits Mock Exam 1

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

class Program
{
    static void Main()
    {
            var n = Console.ReadLine();
            var split = n.ToCharArray();
            int sum = 0;
            int tint = 0;

                foreach (var ch in split)
                {
                    if (Char.IsDigit(ch))
                    {
                        tint = ch - '0';
                        sum += tint;
                        if (sum > 9)
                        {
                            sum = 0;
                        }
                    }

                }

                n = sum.ToString();
                Console.WriteLine(n);

    }
}