template < class Tp, class C = std::list<Tp>, size_t Tag = 5 >
class accountant {};

class  D1 : accountant<double> {};
class  D2 : accountant<double, void, void> {};

class  D2 : accountant<double, void, void> {};

class D1: public Base {};
class D2: public Base {};

accountant<double>