oops ass 5 virtual

#include<bits/stdc++.h>
using namespace std;
class shape
{
    public:
    shape()
    {
    }
    virtual void compute()=0;
};
class triangle: public shape
{
    public:
    double base,height,area;
    triangle()
    {

    }
    triangle(double b1,double h1):shape()
    {
       base=b1;
       height=h1;
    }
    void compute()
    {
      cout<<"Base of triangle: "<<base<<"\n";
      cout<<"Height of triangle: "<<height<<"\n\n";
      area=0.5*base*height;
      cout<<"Area of triangle: "<<area<<"\n";
    }
};
class rectangle:public shape
{
    public:
    double length,width,ar;
    rectangle()
    {

    }
    rectangle(double l1,double w1):shape()
    {
      length=l1;
      width=w1;
    }
    void compute()
    {
      cout<<"length of rectangle: "<<length<<"\n";
      cout<<"width of rectangle: "<<width<<"\n\n";
      ar=length*width;
      cout<<"Area of rectangle: "<<ar<<"\n";
    }
};

int main()
{
   double l,w,h,b;
   int i,x,p=1;
   shape *s;
   triangle t;
   rectangle r;
   while(p)
   {
   cout<<"\nEnter the operation you want to perform: ";
   cout<<"\n1. Area of triangle";
   cout<<"\n2. Area of rectangle";
   cout<<"\n3. Exit";
   cout<<"\n\n Enter your choice: ";
   cin>>x;
   switch(x)
   {
        case 1:
        cout<<"\n\nEnter the dimension of triangle";
        cout<<"\n\nEnter the height of the triangle: ";
        cin>>h;
        cout<<"\nEnter the base of the triangle: ";
        cin>>b;
        t=triangle(h,b);
        s=&t;
        s->compute();
        break;

        case 2:
        {
        cout<<"\n\nEnter the dimension of Rectangle";
        cout<<"\n\nEnter the length of the rectangle: ";
        cin>>l;
        cout<<"\nEnter the width of the rectangle: ";
        cin>>w;
        r=rectangle(l,w);
        s=&r;
        s->compute();
        break;
        }

        case 3:
            exit(0);
        break;

   }
   cout<<"\n\nDo you want to continue(1/0) ";
   cout<<"\nEnter your choice: ";
   cin>>p;
   }
}