import java.util.Scanner;
import java.math.BigDecimal;

public class Main {
	public static void main(String[] args) {
      	Scanner scan = new Scanner(System.in);
      	BigDecimal pi = new BigDecimal("3.14");
		BigDecimal in = new BigDecimal(scan.nextLine());
    	System.out.println(pi.multiply(in).multiply(new BigDecimal("2")));
    }
} import java.util.Scanner; Scanner java.util import java.math.BigDecimal; BigDecimal java.math public class Main {
	public static void main(String[] args) {
      	Scanner scan = new Scanner(System.in);
      	BigDecimal pi = new BigDecimal("3.14");
		BigDecimal in = new BigDecimal(scan.nextLine());
    	System.out.println(pi.multiply(in).multiply(new BigDecimal("2")));
    }
} Main public static void main(String[] args) {
      	Scanner scan = new Scanner(System.in);
      	BigDecimal pi = new BigDecimal("3.14");
		BigDecimal in = new BigDecimal(scan.nextLine());
    	System.out.println(pi.multiply(in).multiply(new BigDecimal("2")));
    } main {
      	Scanner scan = new Scanner(System.in);
      	BigDecimal pi = new BigDecimal("3.14");
		BigDecimal in = new BigDecimal(scan.nextLine());
    	System.out.println(pi.multiply(in).multiply(new BigDecimal("2")));
    } Scanner scan = new Scanner(System.in); scan new Scanner(System.in) BigDecimal pi = new BigDecimal("3.14"); pi new BigDecimal("3.14") BigDecimal in = new BigDecimal(scan.nextLine()); in new BigDecimal(scan.nextLine()) System.out.println(pi.multiply(in).multiply(new BigDecimal("2"))) System.out.println System.out System System.out pi.multiply(in).multiply(new BigDecimal("2")) pi.multiply(in).multiply pi.multiply(in) pi.multiply pi in new BigDecimal("2") String[] args args public class Main {
	public static void main(String[] args) {
      	Scanner scan = new Scanner(System.in);
      	BigDecimal pi = new BigDecimal("3.14");
		BigDecimal in = new BigDecimal(scan.nextLine());
    	System.out.println(pi.multiply(in).multiply(new BigDecimal("2")));
    }
} public class Main {
	public static void main(String[] args) {
      	Scanner scan = new Scanner(System.in);
      	BigDecimal pi = new BigDecimal("3.14");
		BigDecimal in = new BigDecimal(scan.nextLine());
    	System.out.println(pi.multiply(in).multiply(new BigDecimal("2")));
    }
} Main
import java.util.Scanner;
import java.math.BigDecimal;

public class Main {
	public static void main(String[] args) {
      	Scanner scan = new Scanner(System.in);
      	BigDecimal pi = new BigDecimal("3.14");
		BigDecimal in = new BigDecimal(scan.nextLine());
    	System.out.println(pi.multiply(in).multiply(new BigDecimal("2")));
    }
}