using System;

public class Program

{static decimal pi = 3.141592654M;  

 static private decimal vcone(decimal r, decimal h)

 {

    return (1M/3M) * pi * r * r * h;

 }

  static private decimal vcylinder(decimal r, decimal h)

 {

    return pi * r * r * h;

 }

  static private decimal vsphere(decimal r)

 {

    return (4M/3M) * pi * r * r * r;

 }

​

 static private decimal scone(decimal r, decimal h)

    {

        double r2 = (double)r * (double)r;

        double h2 = (double)h * (double)h;

        double slant = Math.Sqrt(r2 + h2);

        return pi * r * r + pi * r * (decimal)slant;

    }

​

    static private decimal ssphere(decimal r)

    {

        decimal r2 = r * r;

        return 4M * pi * r2;

    }

​

    static private decimal scylinder(decimal r, decimal h)

    {

        decimal r2 = r * r;

        decimal h2 = h * h;

        return 2M * pi * r2 + 2M * pi * r * h;

    }

​

    public static void Main()

    {

        start:

        Console.WriteLine("Hello and Welcome to my Volume and Surface Area calculator, press 1 to calculate cone, 2 for cylinder and 3 for sphere.");

        invalid:

        string menu = Console.ReadLine();

        Console.Clear();

        if (menu == "1")

        { 

            Console.WriteLine("Input the radius of the cone");

            decimal r1 = decimal.Parse(Console.ReadLine());

            Console.WriteLine("");

            Console.WriteLine("Input the height of the cone");

            decimal h1 = decimal.Parse(Console.ReadLine());

            Console.WriteLine("");

            Console.WriteLine("Your volume is " + vcone(r1,h1));

            Console.WriteLine("");

            Console.WriteLine("Your surface area is " + scone(r1,h1));

        }

        else if (menu == "2")

        {

            Console.WriteLine("Input the radius of the cylinder");

            decimal r2 = decimal.Parse(Console.ReadLine());

            Console.WriteLine("");

            Console.WriteLine("Input the height of the cylinder");

            decimal h2 = decimal.Parse(Console.ReadLine());

            Console.WriteLine("");

            Console.WriteLine("Your volume is " + vcylinder(r2,h2));

            Console.WriteLine("");

            Console.WriteLine("Your surface area is " + scylinder(r2,h2));

        }

        else if (menu == "3")

        {

            Console.WriteLine("Input the radius of the sphere");

            decimal r3 = decimal.Parse(Console.ReadLine());

            Console.WriteLine("");

            Console.WriteLine("Your volume is " + vsphere(r3));

            Console.WriteLine("");

            Console.WriteLine("Your surface area is " + ssphere(r3));

        }

        else 

        {

            Console.WriteLine("Error! Option not in menu, please try again");

            Console.WriteLine("");

            Console.WriteLine("1 for calculating cone, 2 for cylinder and 3 for sphere");

            goto invalid;

        }

        Console.WriteLine("");

        Console.WriteLine("Press enter to restart and go back to the menu");

        Console.ReadLine();

        Console.Clear();

        goto start;

    }

}