using System;

public class Program

{

    public static void Main()

    {

        foreach (var test in new [] {

            "codegolf.stackexchange.com",

            "codegolf.stackexchange.net",

            "codegolf.stackexchange",

            "codegolf.foo",

            "codegolf",

            "foo",

            "codegolf.com",

            "codegolf.foo.bar",

            "codegolf.stackexchange.com.foo",

            "codegolf.stackexchange.com.foo.bar",

            "foo.stackexchange.com",

            "foo.bar",

            "foo.bar.baz"

        }) {

          string res = $"{test} => ";

          try {

            res += f(test).ToString();

          }

          catch (Exception) {

            res += "Error";

          }

            Console.WriteLine(res);

        }

    }

​

    static bool f(string s){var a=s.Split('.');var b=new[]{"codegolf","stackexchange","com"};int e=0,l=a.Length-1,i=l;for(;0<=i;i--){var c=a[i]!=b[i]?i<l?s[-1]:e=1:0;}return e<1;}

}