class Program
    {
        // Define equation operators here
        enum EquationOperator
        {
            none,
            add,
            subtract,
            multiply,
            divide
        }

        static void Main(string[] args)
        {
            // Instantiate variables here
            int numA;
            int numB;
            EquationOperator equationOperator;

            Console.WriteLine("Welcome to the calculator! Please type an operator!");

            // Check what operator they entered.
            equationOperator = OperatorSelect(Console.ReadLine());

            // For debug purposes.
            Console.WriteLine("The operator you selected was " + equationOperator);

            //Throw an error and exit the program if it isn't a proper operator.
            if (equationOperator == EquationOperator.none)
            {
                Console.WriteLine("That is not a proper operator! Operators are: 'add, subtract, multiply, divide'");
                Console.ReadKey();
                return;
            }
            Console.ReadKey();

        }

        // Check what operator they entered and convert to a proper EquationOperator object.
        // If they don't get one of the cases, return none, which will throw an error.
        static EquationOperator OperatorSelect(string input)
        {
            switch (input)
            {
                case "add":
                    {
                        return EquationOperator.add;
                    }
                case "subtract":
                    {
                        return EquationOperator.subtract;
                    }
                case "multiply":
                    {
                        return EquationOperator.multiply;
                    }
                case "divide":
                    {
                        return EquationOperator.divide;
                    }
                default:
                    {
                        return EquationOperator.none;
                    }
            }
        }



    }