import java.io.*;
import java.math.*;

public class Main {
    public static void main(String args[]) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        PrintWriter pw = new PrintWriter(System.out, true);

        float radius = Float.parseFloat(br.readLine());

        pw.println("S = " + Math.PI * Math.pow(radius,2));
    }
}