CHARACTER SWAPPER

static void Main(string[] args)
        {
            string do_podmianki = Console.ReadLine();
            podmieniacz(do_podmianki);

            Console.ReadKey();
        }
        static string podmieniacz(string do_podmianki)
        {


            char[] letters = do_podmianki.ToCharArray();
            char placeholder_1;
            char placeholder_2;
            placeholder_1 = letters[0];
            placeholder_2 = letters[(letters.Length - 1)];
            letters[0] = placeholder_2;
            letters[(letters.Length - 1)] = placeholder_1;

            string print = "";
            for (int i = 0; i < letters.Length; i++ )
            {
                print += letters[i];
            }
            Console.WriteLine(print);

            return print;


        }