import java.io.*;

public class Circle
{
  public Circle(double r) throws RuntimeException
    {
      if(r <= 0) throw new RuntimeException("The radius must be positive: "
					    + r);
      radius = r;

    }

  public double circumference()
    {
      return 2*Math.PI*radius;
    }

  public double area()
    {
      return Math.PI*radius*radius;
    }

  public double getRadius()
    {
      return radius;
    }

  private double radius;
} // end of Circle class