import java.io.*;
public class kelilinglingkaran
{
public static void main(String[]args)throws IOException
{
double r;
double phi=3.14;

for (int i=0;i<4;i++)
{


BufferedReader br;
br=new BufferedReader(new InputStreamReader(System.in));
System.out.print("Masukan jari-jari Lingkaran = ");
r=Double.parseDouble(br.readLine());
double keliling=2*phi*r;

System.out.println("Keliling lingkaran adalah =" + keliling);

}

}
}