import java.util.*;

public class Main {
	public static void main(String[] args){

		Scanner scan01 = new Scanner(System.in);
		int num = scan01.nextInt();
		scan01.close();

		int mult = num*2;

		double circle= mult * 3.14;

		System.out.println(circle);
	}
} import java.util.*; util.* java public class Main {
	public static void main(String[] args){

		Scanner scan01 = new Scanner(System.in);
		int num = scan01.nextInt();
		scan01.close();

		int mult = num*2;

		double circle= mult * 3.14;

		System.out.println(circle);
	}
} Main public static void main(String[] args){

		Scanner scan01 = new Scanner(System.in);
		int num = scan01.nextInt();
		scan01.close();

		int mult = num*2;

		double circle= mult * 3.14;

		System.out.println(circle);
	} main {

		Scanner scan01 = new Scanner(System.in);
		int num = scan01.nextInt();
		scan01.close();

		int mult = num*2;

		double circle= mult * 3.14;

		System.out.println(circle);
	} Scanner scan01 = new Scanner(System.in); scan01 new Scanner(System.in) int num = scan01.nextInt(); num scan01.nextInt() scan01.nextInt scan01 scan01.close() scan01.close scan01 int mult = num*2; mult num*2 num 2 double circle= mult * 3.14; circle mult * 3.14 mult 3.14 System.out.println(circle) System.out.println System.out System System.out circle String[] args args public class Main {
	public static void main(String[] args){

		Scanner scan01 = new Scanner(System.in);
		int num = scan01.nextInt();
		scan01.close();

		int mult = num*2;

		double circle= mult * 3.14;

		System.out.println(circle);
	}
} public class Main {
	public static void main(String[] args){

		Scanner scan01 = new Scanner(System.in);
		int num = scan01.nextInt();
		scan01.close();

		int mult = num*2;

		double circle= mult * 3.14;

		System.out.println(circle);
	}
} Main
import java.util.*;

public class Main {
	public static void main(String[] args){

		Scanner scan01 = new Scanner(System.in);
		int num = scan01.nextInt();
		scan01.close();

		int mult = num*2;

		double circle= mult * 3.14;

		System.out.println(circle);
	}
}
