static void Main(string[] args)
        {
            // var quad1 = new Quadrillateral(2, 4, 6, 8);
            var quad1 = new Quadrillateral {
                Side1 = 2, Side2 = 4, Side3 = 6, Side4 = 8
            };

            quad1.Perimeter();

            var rect1 = new Rectangle(5, 7);

            rect1.Perimeter();
            rect1.Area();

            var sqr1 = new Square(6);

            sqr1.Perimeter();
            sqr1.Area();
        }