using System;

class Program
{
    static void Main()
    {
        string figure = Console.ReadLine();
        if (figure == "square")
        {
            double a = double.Parse(Console.ReadLine());
            Console.WriteLine(Math.Round(a * a, 3));
        }
        else if (figure == "rectangle")
        {
            double a = double.Parse(Console.ReadLine());
            double b = double.Parse(Console.ReadLine());
            Console.WriteLine(Math.Round(a * b, 3));
        }
        else if (figure == "circle")
        {
            double a = double.Parse(Console.ReadLine());
            Console.WriteLine(Math.Round(Math.PI * a * a, 3));
        }
        else if (figure == "triangle")
        {
            double a = double.Parse(Console.ReadLine());
            double ha = double.Parse(Console.ReadLine());
            Console.WriteLine(Math.Round(a * ha / 2, 3));
        }
    }
}