#include <iostream>

int global_a;

template<typename D>
struct Base {
  int foo() {
    if (global_a)
      return global_a;
    else
      return static_cast<D*>(this)->bar();
  }

  int bar() {
    return 1;
  };
};

struct Derived: public Base<Derived> {
  int bar() {
    return 2;
  };
};


int main (void) {
  Derived d;
  global_a = 5;
  std::cout << "foo() = " << d.foo() << "\n";
  global_a = 0;
  std::cout << "foo() = " << d.foo() << "\n";
}