22 задача

import com.sun.xml.internal.bind.v2.runtime.reflect.opt.Const;

import java.util.Scanner;

public class Main {

    public static void main(String[] args) {


        Scanner scanner =new Scanner(System.in);

          double radius = Double.parseDouble(scanner.nextLine());

       double result=Math.PI*2*radius;

        System.out.println(result);




    }
}