using System;

public class Program

{

    public double Add(double value1, double value2)

    {

        double answer = value1 + value2;

        return answer;

    }

    public double Subtract(double value1, double value2)

    {

        double answer = value1 - value2;

        return answer;

    }

    public double Multiply(double value1, double value2)

    {

        double answer = value1 * value2;

        return answer;

    }

    public double Divide(double value1, double value2)

    {

        double answer = value1 / value2;

        return answer;

    }

    public void Main()

    {

        double value1 = 0; 

        double value2 = 0;

        double answer = 0; 

        Console.WriteLine("Please enter your first value");

        string input1 = Console.ReadLine();

        Console.WriteLine("Please enter the opertator");

        string operation = Console.ReadLine();

        Console.WriteLine("Please enter your second value");

        string input2 = Console.ReadLine();

        double.TryParse(input1, out value1);

        double.TryParse(input2, out value2);

        while (!double.TryParse(input1, out value1)){

            Console.WriteLine("Please re-enter your first value");

            input1 = Console.ReadLine();

            double.TryParse(input1, out value1);

        }

        while (!double.TryParse(input2, out value2)){

            Console.WriteLine("Please re-enter your second value");

            input2 = Console.ReadLine();

            double.TryParse(input2, out value2);

        }

        while (!(operation == "+" || operation == "-" || operation == "*" || operation == "/")){

            Console.WriteLine("Please re-enter the operator");

            operation = Console.ReadLine();

        }

        if (operation == "+"){

            answer = Add(value1, value2);

            Console.WriteLine (answer);

        }

        else if (operation == "-"){

            answer = Subtract(value1, value2);

            Console.WriteLine (answer);

        }

        else if (operation == "*"){

            answer = Multiply(value1, value2);

            Console.WriteLine (answer);

        }

        else if (operation == "/"){

            answer = Divide(value1, value2);

            Console.WriteLine (answer);

        }

        else {

            Console.WriteLine("Invalid operator");

        }

    }

}