using System;

class PruebaHerenciaFigura
{
    public class Figura
    {
        public const double PI = Math.PI;
        protected double x, y;
        
        public Figura ()
        {
        }
        
        public Figura (double x, double y)
        {
            this.x = x;
            this.y = y;
        }
        
        public virtual double Area ()
        {
            return x * y;
        }
    }
    
    public class Circulo : Figura
    {
        public Circulo (double r) : base (r, 0)
        {
        }
        
        public override double Area ()
        {
            return PI * x * x;
        }
    }
    
    public class Esfera : Figura
    {
        public Esfera (double r) : base (r, 0)
        {
        }
        
        public override double Area ()
        {
            return 4 * PI * x * x;
        }
    }
    
    public class Cilindro : Figura
    {
        public Cilindro (double r, double h) : base (r, h)
        {
        }
        
        public override double Area ()
        {
            return 2 * PI * x * x + PI + x + y;
        }
    }
    
    public static void Main ()
    {
        double r = 7.0, h = 11.0;
        
        Figura[] figuras = new Figura[3];
        
        figuras[0] = new Circulo (r);
        figuras[1] = new Esfera (r);
        figuras[2] = new Cilindro (r, h);
        
        // Muestra resultados.
        // La invocaciön del método Area ocurre polimófircamente
        Console.WriteLine ("Área del círculo: {0:F2}", figuras[0].Area ());
        Console.WriteLine ("Área de la esfera: {0:F2}", figuras[1].Area ());
        Console.WriteLine ("Área del cilindro: {0:F2}", figuras[2].Area ());
    }
}