using System;

using System.Collections.Generic;

​

enum TriangleType : byte {Square, Acute, Obtuse}

enum QuadrilateralType : byte {Square, Rectangle}

​

abstract class TwoDShape

{

    public int NumSides {get; protected set;}

    protected int[] sides;

    public abstract double Area();

    public override string ToString()

    {

        return string.Format("Our figure has {0} side{1}",this.NumSides,this.NumSides > 1 ? "s" : ""); 

    }

    public TwoDShape(int numSides,params int[] num)

    {

        this.NumSides = numSides;

        this.sides    = new int[numSides];

        if(num.Length == numSides)

            for(int i = 0; i < num.Length;i++)

               this.sides[i] = num[i];

        else

            throw new Exception("Count of parameters on equal count of sides!");

    }

}

​

class Triangle : TwoDShape

{

    public TriangleType Type {get; protected set;}

    public Triangle(TriangleType style,params int[] num) : base(3,num)

    {

        this.Type = style;

    }

    public override double Area()

    {

        double halfPerim = (this.sides[0] + this.sides[1] + this.sides[2]) /2;

        return Math.Sqrt(halfPerim * (halfPerim - this.sides[0]) * (halfPerim - this.sides[1]) * (halfPerim - this.sides[2]));

    }

    public int this[int index]

    {

        get

        {

            return this.sides[index];

        }

        set

        {

            this.sides[index] = value;

        }

    }

    public override string ToString()

    {

        string result = "";

        for(int i = 0; i < this.sides.Length;i++)

        {

            result += string.Format("\nSide {0} : {1}", (char)('A'+i),this.sides[i]);

        }

        return string.Format("Triangle\n\nType: {0}\n {1}\n\nArea of triangle: {2}",this.Type,result,this.Area());

    }

}

​

​

abstract class Quadrilateral : TwoDShape

{

    public Quadriliteral()

    {

        this.NumSides = 4;

        this.sides = new int[4];

    }

}

​

​

public class Program

{

    public static void Main()

    {

        int[] sides = {8,6,10};

        TwoDShape tri = new Triangle(TriangleType.Square,sides);        

​

        Console.WriteLine(tri.ToString());      

    }

}