void ParseInput(string input)
        {
            if (inputIsntGoingToBeCalculated(input))
            {
                return;
            }
            var p = new Parser(input);
            try
            {
                p.ParseInput();
                var results = p.results;
                char operand = p.operand;
                response = CalculateResponse(results, operand);

                Stack.lastResponse = response;
                Stack.lastQuestion = staticInput;
            }
            catch (ArgumentException e)
            {
                response = e.Message;
                return;
            }
        }