import cs1.Keyboard;
import java.lang.Math;
/**
   Calculate circumference given radius.
   @author Greg Vogl
   last modified 2003-10-06
*/
public class Circumference
{
   /**
      Calculate circumference given radius.
   */
   public static void main (String[] args) 
   {
      // get input
      System.out.println("Calculate circumference given radius.");
      System.out.println("Enter the radius and press Enter.");
      double radius = Keyboard.readFloat();

      // calculate circumference
      double circumference = 2 * Math.PI * radius;

      // output results
      System.out.println("The circumference is " + circumference + ".");
   }
}