static void Main(string[] args)
        {
            BankAccount benben = new BankAccount("Benson", (decimal)17.25);

            Console.WriteLine(benben.ShowUserNameAndBalance());

            BankAccount penpen = new BankAccount("Peter", (decimal)15000.5);

            Console.WriteLine(penpen.ShowUserNameAndBalance());

            BankAccount zenzen = new BankAccount("Zinedin", (decimal) - 11.9);

            Console.WriteLine(zenzen.ShowUserNameAndBalance());

            Console.ReadKey();
        }
        static void Main(string[] args)
        {
            BankAccount marija = new BankAccount("Marija Bondarenko", -0.1);

            marija.ShowUserNameAndBalance();
        }