using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace CalculatorApp
{
    class Program
    {
        static void Main(string[] args)
        {
            double num1, num2, result;
            string operation;

            Console.WriteLine("C# Calculator\n");

            Console.Write("Enter first number: ");
            num1 = Convert.ToDouble(Console.ReadLine());

            Console.Write("Enter an operator (+, -, *, /): ");
            operation = Console.ReadLine();

            Console.Write("Enter second number: ");
            num2 = Convert.ToDouble(Console.ReadLine());

            switch (operation)
            {
                case "+":
                    result = num1 + num2;
                    break;
                case "-":
                    result = num1 - num2;
                    break;
                case "*":
                    result = num1 * num2;
                    break;
                case "/":
                    if (num2 != 0)
                    {
                        result = num1 / num2;
                    }
                    else
                    {
                        Console.WriteLine("Division by zero is not allowed.");
                        return;
                    }
                    break;
                default:
                    Console.WriteLine("Invalid operator.");
                    return;
            }

            Console.WriteLine($"Result: {result}");
            Console.ReadKey();
        }
    }
}