using System;

public class SimpleCalculator

{

    public static void Main()

    {

        int num1;

        int num2;

        int operation = 1;

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

        num1 = Convert.ToInt32(Console.ReadLine());

        Console.WriteLine("");

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

        num2 = Convert.ToInt32(Console.ReadLine());

        Console.WriteLine("Choose a operation");

        Console.WriteLine("");

        Console.WriteLine("1 - Addition(+)");

        Console.WriteLine("2 - Subtraction(-)");

        Console.WriteLine("3 - Multiplication(*)");

        Console.WriteLine("4 - Division(/)");

        do{

        operation = Convert.ToInt16(Console.ReadLine());

         if(operation == 1|operation ==2|operation ==3|operation ==4){

            Console.WriteLine("");

            Console.WriteLine("The answer is "+ Operation(num1, num2, operation));

        }else{

        Console.WriteLine("");

        Console.WriteLine("Please input a valid operation.");

        }

        }while(operation != 1&&operation !=2&&operation !=3&&operation !=4);

    }

     public static int Operation(int num1, int num2, int operation){

         int ans;

        if(operation == 1){

            ans = num1 + num2;

            return ans;

        }else if(operation == 2){

            ans = num1 - num2;

            return ans;

            }else if(operation == 3){

                ans = num1 * num2;

            return ans;

                }else if(operation == 4){

                        ans = num1 / num2;

            return ans;

                    }

        return 0;

    }

}