using System;

public class Program

{

    public static void CaTourneFor ()

    {

        for (int i=0; i<5; i++)

        {

        Console.WriteLine("ca tourne");

        }

    }

    public static double SurfCarre (double cote)

    {

        double surface = cote*cote;

        return surface;

    }

    public static void ex2()

    {

        Console.WriteLine("entrez le coté du carré");

        double cote = Convert.ToDouble(Console.ReadLine());

        double surface = SurfCarre (cote);

        Console.WriteLine(surface);

    }

    public static double SurfCercle (double rayon)

    {

        return rayon*rayon*Math.PI;

    }

    public static void testsurfcercle ()

    {

        Console.WriteLine("entrez le rayon du cercle");

        double rayon = Convert.ToDouble(Console.ReadLine());

        double surface = SurfCercle(rayon);

        Console.WriteLine("La surface du cercle est " + surface);

    }

    public static double cotecarre (double surface)

    {

        double cote = Math.Sqrt(surface);

        return cote;

    }

    public static void ex6 (double cote)

    {

        Console.WriteLine("entrez le rayon du cercle");

        double rayon = Convert.ToDouble(Console.ReadLine());

        double surface = SurfCercle(rayon);

        Console.WriteLine("La surface du cercle est " + surface);

        double cote = cotecarre (surface);

    }

    public static void Main()

    {

        //CaTourneFor();

        //ex2();

        testsurfcercle ();

    }

}