text: #include<iostream>
  #include<string>
  #include<vector>
  #include<cctype>
  #include<stdexcept>
  using std::istream; using std::ostream;
  using std::string ; using std::cin ; using std::cout ; using std::cin ; using std::endl; using std::vector; using std::runtime_error; using std::end; using std::begin;
  
  class Status {
  public:
      static int count;
      unsigned returnserial(){return book.returnSerial();}
      unsigned returnid(){return book.returnid();}
      void update(bool,Book  );
      Status() {count = 0;}
      void show()
      {
          cout<<endl<<book;
      }
  private:
      Book book;
      bool status ;
  };
  void Status::update( bool t,Book b)
  {
      book = b;
      status = t;
      if(t)
          Status::count--;
      else
          Status::count++;
  }
  int Status::count= 0;
  