import java.util.Scanner;

/**
 * Created by Atanas on 17/01/2017.
 */
public class p13_Sharea {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        String shape = scanner.nextLine();

        if (shape.equals("square")){
            double a = Double.parseDouble(scanner.nextLine());
            double b = a * a;
            System.out.printf("%.3f%n", b);
        } else if (shape.equals("circle")){
            double a = Double.parseDouble(scanner.nextLine());
            double b = a * a * Math.PI;
            System.out.printf("%.3f%n", b);
        } else if (shape.equals("rectangle")){
            double a = Double.parseDouble(scanner.nextLine());
            double b = Double.parseDouble(scanner.nextLine());
            double c = a * b;
            System.out.printf("%.3f%n", c);
        } else if (shape.equals("triangle")){
            double a = Double.parseDouble(scanner.nextLine());
            double b = Double.parseDouble(scanner.nextLine());
            double c = (a * b) / 2;
            System.out.printf("%.3f%n", c);
        }
    }