using System;

public class Program

{

    static private double hyp(double a, double b) 

    {

        double a2 = a * a;

        double b2 = b * b;

        return Math.Sqrt(a2 + b2);

    }

    static private double lrt(double a, double c)

    {

        double a2 = a * a;

        double c2 = c * c;

        return Math.Sqrt(c2 - a2);

    }

    public static void Main()

    {

        string restart = "This is wrong.";

        while (restart != "q")

        {

            start:

            Console.Clear();

            Console.WriteLine("Press 1 if you are missing the hypotenuse and 2 if you are misssing the leg");

            byte choice = byte.Parse(Console.ReadLine());

            if (choice == 1)

            {

                Console.WriteLine("Please enter the length of your first leg.");

                double leg1 = double.Parse(Console.ReadLine());

                Console.WriteLine("Please enter the length of your second leg.");

                double leg2 = double.Parse(Console.ReadLine());

                Console.WriteLine("The length of the hypotenuse of your right triangle is: " + hyp(leg1, leg2).ToString("##.##"));

    }

    else

    {

    Console.WriteLine("Please press 1 or 2.");

    goto start;

    }

    Console.WriteLine("press q to quit the program or any other key to continue.");

    restart = Console.ReadLine();

    }

    }

}

​