Areas

import java.util.Scanner;

public class Areas {
    public static void main(String[] agrs) {
        Scanner scanner = new Scanner(System.in);
        String figure = scanner.nextLine();

        if (figure.equals("square")) {
            double a = Double.parseDouble(scanner.nextLine());
            System.out.println(a * a);
        } else if (figure.equals("rectangle")) {
            double a = Double.parseDouble(scanner.nextLine());
            double b = Double.parseDouble(scanner.nextLine());
            System.out.println(a * b);
        } else if (figure.equals("triangle")) {
            double a = Double.parseDouble(scanner.nextLine());
            double h = Double.parseDouble(scanner.nextLine());
            System.out.println((a*h)/2);
        }else if(figure.equals("circle")){
            double r = Double.parseDouble(scanner.nextLine());
            System.out.println(Math.PI*r*r);
        }
    }
}