test

interface figure{
    double area();
    double perimetr();
}

class triangle implements figure{
    double a,b,c;
    triangle(double x,double y,double z){
        a=x;b=y;c=z;
    }
    triangle(){
        a=b=c=0;
    }
    public double area(){
        double p=(a+b+c)/2.0;
        return Math.sqrt(p*(p-a)*(p-b)*(p-c));
    }
    public double perimetr(){
        return a+b+c;
    }
}

class megatriangle extends triangle{
    megatriangle(double a,double b,double c){
        super(a,b,c);
    }
    public double R(){
        return 0.25*a*b*c/area();
    }
}

public class geom {
    public static void main(String args[]){
         megatriangle t=new megatriangle(3,4,5);
         System.out.println(t.area()+" "+t.perimetr()+" "+t.R());
    }
}