#include <vector>
#include <iostream>

template<typename T, typename CONT = std::vector<T>>
class stack {
public:
  stack();
  ~stack();
  auto push(T&) -> void;
  auto pop() -> void;
  auto top() -> T&;
  auto top() const -> T const&;
  static int num_stacks_;

private:
  CONT stack_;
};

template<typename T, typename CONT>
int stack<T, CONT>::num_stacks_ = 0;

template<typename T, typename CONT>
stack<T, CONT>::stack() {
  num_stacks_++;
}

template<typename T, typename CONT>
stack<T, CONT>::~stack() {
  num_stacks_--;
}

auto main() -> int {
  auto fs = stack<float>{};
  stack<int> is1, is2, is3;
  std::cout << stack<float>::num_stacks_ << "\n";
  std::cout << stack<int>::num_stacks_ << "\n";
}