#include <iostream>
#include <vector>

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

private:
  std::vector<T> stack_;
};

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

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

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

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