using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Would you like to add (enter +), subtract (enter -),\n multiply (enter *) or divide (enter / )?");

        string operation = Console.ReadLine();

        Console.WriteLine("Enter your first number: ");

        string Num = Console.ReadLine();

        double Num1 = Convert.ToDouble(Num);

        string x;

        x = Convert.ToString((Num1.GetType()));

        if (x != "System.Double") {

            Console.WriteLine("error");

        }

        else {

            //double Num2;

            Console.WriteLine("Enter your second number: ");

            double Num2 = Convert.ToDouble(Console.ReadLine());

            string y;

            y = Convert.ToString((Num2.GetType()));

            if (y != "System.Double") {

                Console.WriteLine("error");

            }

            else {

                if (operation == "+") {

                    double ans = Num1 + Num2;

                    Console.WriteLine(Num1 + " + " + Num2  + " = " + ans);

                }

                else if (operation == "-") {

                    double ans = Num1 - Num2;

                    Console.WriteLine(Num1 + " - " + Num2 + " = " + ans);

                }

                else if (operation == "*") {

                    double ans = Num1 * Num2;

                    Console.WriteLine(Num1 + " * " + Num2 + " = " + ans);

                }

                else if (operation == "/") {

                    double ans = Num1 / Num2;

                    Console.WriteLine(Num1 + " / " + Num2 + " = " + ans);

                }

                else {

                    Console.WriteLine("error");

                }

    }

}}}