#include <iostream>
#include <string>
#include <vector>

using namespace std;

struct A {
  public:
    virtual string s() { return "a"; }
};

class B : public A {
  public:
    string s() { return "b"; }
};

B
make_b()
{
  B b;
  return b;
}

A
make_a()
{
  return make_b();
}

int
main(void)
{
  vector<A> x;
  B b = make_b();
  x.push_back(b);
  cout << x[0].s() << endl;
  B c;
  x.push_back(c);
  cout << x[1].s() << endl;

  return 0;
}