using System;

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;               

public class Geometry3D

{

    public static void Main()

    {//Обем на правоъгълник

    public static double SquarePerimeter(double side);

    }

    {

    return side * v = a.a.a = 3a

    }

    //Лице на пълна повърхнина

    public static double SquareArea(double side);

    {

    return side * side

    }

}