#include <iostream>
#include <cmath>
using namespace std;


class Shape
{
public:
    virtual Shamename() const=0;
    virtual area() const=0;
};


class Circle:public Shape
{
public:
    Circle(double r):radius(r) {}
    virtual Shamename() {cout<<"Circle:"<<endl;}
    virtual double area(){return 3.1415926*radius*radius;}
protected:
    double radius;
};
class Rectangle:public Shape
{
public:
    Rectangle(double a,double b):length(a),with(b) {}
    virtual Shamename(){cout<<"Rectangle:"<<endl;}
    double area() {return length*with;}
protected:
    double length,with;
};
class Triangle:public Shape
{
public:
    Triangle(double a,double b,double c):bord1(a),bord2(b),bord3(c) {}
    virtual Shamename(){cout<<"Rectangle:"<<endl;}
    double area()
    {
        double s=(bord1+bord2+bord3)/2;
        return sqrt(s*(s-bord1)*(s-bord2)*(s-bord3));
    }
protected:
    double bord1,bord2,bord3;
};
void printArea(const Shape &s)
{
    cout<<s.Shamename()<<endl;
    cout<<s.area()<<endl;
}
void main()
{
      Circle c1(2);
      printArea(c1);
}
错在哪里啊