using System;

public class Program

{

    public static void Main()

    {

        string figure = Console.ReadLine();

        double area = 0;

        if (figure == "triangle")

        {

            double side = double.Parse(Console.ReadLine());

            double height = double.Parse(Console.ReadLine());

            area = GetTriangleArea(side,height);

        }

        if (figure == "square")

        {

            double side = double.Parse(Console.ReadLine());

            area = GetSquareArea(side);

​

        }

        if (figure == "rectangle")

        {

            double width = double.Parse(Console.ReadLine());

            double height = double.Parse(Console.ReadLine());

            area = GetRectangleArea( width, height);

        }

        if (figure == "circle")

        {

            double radius = double.Parse(Console.ReadLine());

            area = GetCyrcleArea(radius);

        }

        Console.WriteLine("{0:f2}",area);

    }

    public static  double GetTriangleArea(double side,double height)

    {

        double area = (side*height)/2;

        return area;

    }

    public static  double GetSquareArea(double side)

    {

        double area = side*side;

        return area;

    }

    public static  double GetRectangleArea(double width,double height)

    {

        double area = width*height;

        return area;

    }

    public static  double GetCyrcleArea(double radius)

    {

        double area = Math.PI*radius*radius;

        return area;

    }

}