import java.util.Scanner;

public class nauka {

	public static void skan() {
		System.out.println("podaj promien");
		Scanner sk = new Scanner(System.in);
		double r = sk.nextDouble();
	}

	public static double pole(double r) {


		double p = 3.14 * r*r;
		return p;

	}
	public static void main(String[] args) {
		skan();
		System.out.println("pole koła wynosi" + pole());
	}
}