using System;

namespace Area_Of_Figures
{
    class Program
    {
        static void Main(string[] args)
        {
            var figure = Console.ReadLine();
            double num = 0;

            double num2 = 0;

            if (figure == "square")
            {
                num = double.Parse(Console.ReadLine());
                Console.WriteLine(num * num);
            }
            else if (figure == "rectangle")
            {
                num = double.Parse(Console.ReadLine());
                num2 = double.Parse(Console.ReadLine());
                Console.WriteLine(num*num2);
            }
            else if (figure == "circle")
            {

                num2 = double.Parse(Console.ReadLine());

                Console.WriteLine(Math.PI * num2 * num2);
            }

            else if (figure == "triangle")
            {
                 num = double.Parse(Console.ReadLine());
                  num2 = double.Parse(Console.ReadLine());


                Console.WriteLine(num*num2/2);
            }




        }
    }
}