using System;

public class Program

{

    public static void Main()

    {

        bool again = true;

        while(again == true)

        {

            //Ask user to make a choice

            Console.WriteLine("\nWhat would you like to do... \na) Addition \nb) Subtraction \nc) Multiplication \nd) Division \ne) exit" );

            //User input converted to upper case

            string choice = Console.ReadLine().ToUpper();

            if (choice.Equals("A")) // If 'A' then take numbers and perform addition

            {

                Console.WriteLine("Please enter a number: ");

                int firstNum = int.Parse(Console.ReadLine());

                int secondNum = int.Parse(Console.ReadLine());

                int result = firstNum + secondNum;

                Console.WriteLine(firstNum + " + " + secondNum + " = " + result);

            }

            else if (choice.Equals("B")) // If 'A' then take numbers and perform subtraction

            {

                Console.WriteLine("Please enter a number: ");

                int firstNum = int.Parse(Console.ReadLine());

                int secondNum = int.Parse(Console.ReadLine());

                int result = firstNum - secondNum;

                Console.WriteLine(firstNum + " - " + secondNum + " = " + result);

            } 

            else if (choice.Equals("C")) // If 'C' then take numbers and perform multiplication

            {

                Console.WriteLine("Please enter a number: ");

                int firstNum = int.Parse(Console.ReadLine());

                int secondNum = int.Parse(Console.ReadLine());

                int result = firstNum * secondNum;

                Console.WriteLine(firstNum + " x " + secondNum + " = " + result);

            } 

            else if (choice.Equals("D")) // If 'D' then take numbers and perform division

            {

                Console.WriteLine("Please enter a number: ");

                int firstNum = int.Parse(Console.ReadLine());

                int secondNum = int.Parse(Console.ReadLine());

                int result = firstNum / secondNum;

                Console.WriteLine(firstNum + " / " + secondNum + " = " + result);

            } 

            else if (choice.Equals("E")) // If 'E' then exit loop

            {

                Console.WriteLine("Thank you");

                again = false;

            }

            else

            {

                Console.WriteLine(choice + " is not a valid option. Choose a, b, c, or d. ");

            } 

        }

    }

}