Show the output of the following program and explain it.

#include

using namespace std;

class A{

public:

int f(){ return 1; }

virtual int g(){ return 2; }

};

class B : public A{

public:

int f(){ return 3; }

int g(){ return 4; }

};

class C : public A{

public:

int g(){ return 5; }

};

int main(){

A *pa;

A a; B b; C c;

pa = &a; cout << pa->f() << endl; cout << pa->g() << endl << endl;

pa = &b; cout << pa->f() + pa->g() << endl << endl;

pa = &c; cout << pa->f() << endl; cout << pa->g() << endl << endl;

system("pause");

return 0;

}