#include <iostream>

class AbstractBase {
 public:
  virtual ~AbstractBase() = default;

  virtual void f() = 0;
};

class C1 : public AbstractBase {
 public:
  void f() override {
    std::cout << "From C1" << std::endl;
  }
};

class C2 : public AbstractBase {
 public:
  void f() override {
    std::cout << "From C2" << std::endl;
  }
};

AbstractBase& CreateC(int i) {
  static auto c1 = C1();
  static auto c2 = C2();
  if (i == 0) {
    return c1;
  } else {
    return c2;
  }
}

int main() {
  AbstractBase& c = CreateC(0);
  c.f();
  c = CreateC(1);
  c.f();
  return 0;
}