#include <memory>
template <typename T>
class threadsafe_queue {
public:
  threadsafe_queue();
  threadsafe_queue(const threadsafe_queue&);
  threadsafe_queue& operator=(const threadsafe_queue&) = delete;

  void push(T new_value);

  bool try_pop(T& value);
  std::shared_ptr<T> try_pop();

  void wait_and_pop(T& value);
  std::shared_ptr<T> wait_and_pop();

  bool empty() const;
};

int
main()
{
}