c++ constructor, copy constructor, operator =

// list::push_back

#include <iostream>

#include <list>

class element{

private:

    int number;

public:

    element(int number){

        this->number = number;

        std::cout << "constructor used" << std::endl;

    }

    element(const element&){

       std::cout << "copy constructor used" << std::endl;

    }

    element& operator=(const element& element_instance){

        std::cout << element_instance.number << "operator=" << std::endl;

        this->number = element_instance.number;

        return *this;

    }

    int get_number(){

        return this->number;

    }

    ~element(){

        std::cout << this->number << std::endl;

        this->number = ;

        std::cout << "destructor used" << std::endl;

    }

};

int main ()

{

  std::list<element> mylist;

  int myint;

  std::cout << "Please enter some integers (enter 0 to end):\n";

  do {

    std::cin >> myint;

    element* element_instance = new element(myint);

    mylist.push_back (*element_instance);

    delete element_instance;

  } while (myint);

  //std::cout << "mylist stores " << mylist.size() << " numbers.\n";

  std::cout << "first number:" << (mylist.front().get_number()) << std::endl;

  return ;

}