using System;

public class Program

{

    abstract class Figure

    {

        protected double S_quare {get;set;}

        protected double P_erimeter {get;set;}

        public virtual double calcSquare()

        {

            return 0;

        }

        public virtual double calcPerim()

        {

            return 0;

        }

        public virtual void show()

        {

            Console.WriteLine("Figure: Null. Square: NULL. Perimeter: NULL.");

        }

    }

​

    class Square : Figure

    {

        private double Side {get;set;}

        public Square(double side)

        {

            Side = side;

        }

        public override double calcSquare()

        {

            S_quare = Side*Side;

            return S_quare;

        }

        public override double calcPerim()

        {

            P_erimeter = 4*Side;

            return P_erimeter;

        }

        public override void show()

        {

            Console.WriteLine("Figure: Square. Square: " + S_quare + ". Perimeter: " + P_erimeter + ".");

        }

    }

    class RTriangular : Figure

    {

        private double Side {get;set;}

        public RTriangular(double side)

        {

            Side = side;

        }

        public override double calcSquare()

        {

            S_quare = Side*Side*Math.Sqrt(3)/4;

            return S_quare;

        }

        public override double calcPerim()

        {

            P_erimeter = 3*Side;

            return P_erimeter;

        }

        public override void show()

        {

            Console.WriteLine("Figure: Right triangular. Square: " + S_quare + ". Perimeter: " + P_erimeter + ".");

        }

    }

    class Rectangular : Figure

    {

        private double Side1;

        private double Side2;

        public Rectangular(double side1, double side2)

        {

            Side1 = side1;

            Side2 = side2;

        }

        public override double calcSquare()

        {

            S_quare = Side1*Side2;

            return S_quare;

        }

        public override double calcPerim()

        {

            P_erimeter = 2*Side1+2*Side2;

            return P_erimeter;

        }

        public override void show()

        {

            Console.WriteLine("Figure: Rectangular. Square: " + S_quare + ". Perimeter: " + P_erimeter + ".");

        }

    }

    public static void Main()

    {

        double a = 5;

        double b = 8;

        RTriangular triang = new RTriangular(a);

        triang.calcPerim();

        triang.calcSquare();

        triang.show();

        Square square = new Square(a);

        square.calcPerim();

        square.calcSquare();

        square.show();

        Rectangular rect = new Rectangular(a,b);

        rect.calcPerim();

        rect.calcSquare();

        rect.show();

    }

}