static void Main(string[] args)
        {
            var quad1 = new Quadrillateral {
                Leg1 = 2, Leg2 = 4, Leg3 = 6, Leg4 = 8
            };

            quad1.GetPerimeter();

            var rect1 = new Rectangle(5, 7)
            {
            };

            rect1.GetPerimeter();
            rect1.GetArea();

            var sq1 = new Square(7)
            {
            };

            sq1.GetPerimeter();
            sq1.GetArea();
        }