using System;

public class Program

{

    public static void Main()

    {

        int a,b;

        Console.WriteLine("Please Enter Num1 Value:");

        bool isvalidInt = int.TryParse (Console.ReadLine(), out a);

        Console.WriteLine("Please Enter Num2 Value:");

        bool isvalidInt2 = int.TryParse (Console.ReadLine(), out b);

        if(isvalidInt && isvalidInt2)

        {

            perform(a,b);

        }

        else if (isvalidInt)

        {

        Console.WriteLine("Enter valid num2..!");

        }

        else if (isvalidInt2)

        {

        Console.WriteLine("Enter valid num1..!");

        }

        else

        {

        Console.WriteLine("Enter valid num1 and num2..!");

        }

    }

        static void perform(int a, int b)

        {

            int c,d;

            Console.WriteLine("Do you want Perform Arithmetic operation? if you want add Press 1, If u want sub Press 2, If u want Multiply Press 3, If u want Divide Press 4.");

            c = Convert.ToInt32(Console.ReadLine());

            if(c == 1)

            {

                Console.WriteLine(a+b);

            }

            else if (c == 2)

            {

                Console.WriteLine(a-b);

            }

            else if (c == 3)

            {

                Console.WriteLine(a*b);

            }

            else if (c == 4)

            {

                Console.WriteLine(a/b);

            }

            else

            {

                Console.WriteLine("You Press incorrect Number...Press 1,2,3 and 4 only");

                perform(a,b);

            }

            Console.WriteLine("Do you want continue? if you want continue press 5. if u want stop press 6");

            d = Convert.ToInt32(Console.ReadLine());

            if(d == 5)

            {

                Main();

            }

            else if (d == 6)

            {

                Console.WriteLine("Thank you.. BYE");

            }

            else

            {

                Console.WriteLine("You Press incorrect Number...Press 3 or 4 only. Try again");

                Main();

            }

        }

    }