template <class T>
struct StatAllocator {
   using value_type = T;
   using propagate_on_container_copy_assignment = std::false_type;
   using propagate_on_container_move_assignment = std::true_type;
   using propagate_on_container_swap = std::true_type;

   unsigned m_id;
   std::size_t* m_allocated;

   explicit StatAllocator(unsigned id = 0, std::size_t* allocated = nullptr)
       : m_id(id)
       , m_allocated(allocated)
   {}

   template <class U>
   StatAllocator(const StatAllocator<U>& other)
       : m_id(other.m_id)
       , m_allocated(other.m_allocated)
   {}
   template <class U>
   StatAllocator& operator=(const StatAllocator<U>& other) {
       m_id = other.m_id;
       m_allocated = other.m_allocated;
   }

   template <class U>
   bool operator==(const StatAllocator<U>& other) const {
       return m_id == other.m_id;
   }
   
   T* allocate(std::size_t n) {
       if (m_allocated)
           *m_allocated += sizeof(T) * n;
       return reinterpret_cast<T*>(new…