import java.io.IOException; import java.util.Scanner; import java.util.Locale;

public class Main {

public static void main(String[] args) throws IOException {

    Locale.setDefault(Locale.US);
    Scanner ler = new Scanner(System.in);

    double raio = ler.nextDouble();
    double pi = 3.14159;
    double area = pi * Math.pow(raio, 2);

    System.out.printf("A=%.4f%n", area);

    ler.close();
}

}