Child class destructor not getting called

Question

I have the following C++ program :

#include <iostream>
using namespace std;
class A
{
public:
    A()
    {
        cout << "A constructor" << endl;
    }
    ~A()
    {
        cout << "A destructor" << endl;
    }
};
class B : public A
{
public:
    B()
    {
        cout << "B constructor" << endl;
    }
    ~B()
    {
        cout << "B destructor" << endl;
    }
};
int main()
{
    A a1;
    A *a2 = new B();
    delete a2;
}

On running the output is

A constructor
A constructor
B constructor
A destructor
A destructor

I don't understand the output.
A a1; --> this calls A constructor
A *a2 = new B();--> This should call A constructor which in turn should call B constructor
delete a2;

Now, in the end, I see two A destructor calls. But no B destructor call. Sinde the pointer a2 points to an object B. There should have been a call to B destructor before the program exits. What could be the reason that B destructor didn't get called?