using System;

using System.Linq;

using System.Collections.Generic;

public class Program

{

    private static string OnlyDigits(string input) 

    {

        var chars = input.Where(char.IsDigit).ToArray();

        return new string(chars);

    }

    private static string Filter(string input) 

    {   

        switch (input.Length) 

        {           

            case 10: return input;

            case 11: 

                if (input.StartsWith("1")) return input.Substring(1);   

                goto default;

            default:

                return "0000000000";

        }

    }

    public static void Main()

    {

        var list = new List<string>() {

            "123",

            "(1234567890}",

            "11234567890"

        };

        var filtered = list.Select(OnlyDigits).Select(Filter).ToList();

        filtered.ForEach(Console.WriteLine);    

    }

}