using System;
namespace ConsoleApp1
{
    class Program
    {
        static void Main()
        {
            var fig = Console.ReadLine();
            if(fig == "square")
            {
                var a = double.Parse(Console.ReadLine());
                var area = a * a;
                Console.WriteLine(Math.Round(area, 3));
            }
            if (fig == "rectangle")
            {
                var a = double.Parse(Console.ReadLine());
                var b = double.Parse(Console.ReadLine());
                var area = a * b;
                Console.WriteLine(Math.Round(area, 3));
            }
            if (fig == "circle")
            {
                var a = double.Parse(Console.ReadLine());
                var area = Math.PI * (a * a);
                Console.WriteLine(Math.Round(area, 3));
            }
            if (fig == "triangle")
            {
                var a = double.Parse(Console.ReadLine());
                var b = double.Parse(Console.ReadLine());
                var area = (a * b) / 2;
                Console.WriteLine(Math.Round(area, 3));
            }
        }
    }
}