import java.util.Scanner;

public class ExamPreparation {
    public static void main(String[] args) {

        Scanner scanner = new Scanner(System.in);

        String typeGeometricForm = scanner.nextLine();

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

    }

}