interface shape{
double PI=3.14159;
abstract double area();
}
class Circle implements shape{
double radius;
public Circle(double r){
radius=r;
}
public double area(){
return PI*radius*radius;
}
}
public class InterfaceDemo{
public static void main(String args[]){
	   Circle cir=new Circle(10);
	   System.out.println("Circle area="+cir.area());
}
}