import java.util.Scanner;
public class perimeterOfCircle
{
    public static void main(String args[])
    {
        Scanner sc=new Scanner(System.in);
        System.out.println("Enter radius of circle");
        double r=sc.nextDouble();
        double pi=22/7;
        /*Formula of perimeter of circle =2*pi*radius of circle */
        double perimeter=2*pi*r;
        System.out.println("perimeter of circle="+perimeter);
     }
}