#include <stack>
#include <iostream>
#include <utility>
 using namespace std;
class Node
{
public:
    Node(int num) : _num(num), _next(NULL){}
    friend class List;
private:
    int _num;
    Node* _next;
};

class List
{
public:
    List() : _root(NULL){}
    void add(int rhs)
    {
        if (!_root)
        {
            _root = new Node(rhs);
        }
        else
        {
            Node* tmp = _root;
            while (tmp->_next)
            {
                tmp = tmp->_next;
            }
            tmp->_next = new Node(rhs);
        }
    }
    void print() const
    {
        Node* tmp = _root;
        while (tmp)
        {
            cout << tmp->_num << "  ";
            tmp = tmp->_next;
        }
        cout << endl;
    }

    void doubling() // udvoit kazhdoe znachenie
    {
        Node* tmp = _root;
        while (tmp)
        {
            tmp->_num *= 2;
            tmp = tmp->_next;
        }
    }
    ~List()
    {
        Node* tmp = _root;
        while (tmp)
        {
            _root = tmp->_next;
            delete tmp;
            tmp = _root;
        }
    }
private:
    Node* _root;
};

int main()
{
    List lst;
    lst.add(7);
    lst.doubling();
    lst.add(3);
    lst.doubling();



    lst.print();
    return 0;
}