using System;
        using System.Collections.Generic;
        using System.Linq;
        using System.Text;
        using System.Threading.Tasks;

        namespace geomtry_calc
        {
class Program
{ static void vuvedi_dvechisla(string vid, double one,double two)
{
    if (vid == "triangle") { double area = one * two / 2; Console.WriteLine($"{area:f2}"); }
    else if (vid == "rectangle") { double area = one * two; Console.WriteLine($"{area:f2}"); }

}
    static void vuvedi_ednochisla(string vid, double one)
    {
        if (vid == "square") { double area = one * one; Console.WriteLine($"{area:f2}"); }
        else if (vid == "circle") {double circleArea = 3.14159265359; double area = one *one*circleArea; Console.WriteLine($"{area:f2}"); }

    }
    static void Main(string[] args)
    {
        string type = Console.ReadLine();
        double one = double.Parse(Console.ReadLine());

        if (type == "triangle" || type == "rectangle"){
            double two = double.Parse(Console.ReadLine());
            vuvedi_dvechisla(type,one,two);
        }
        else vuvedi_ednochisla(type, one);
    }
}
}