#include <iostream>

using namespace std;

template <class type> class list {
public:

    void insert ()

private:
    class list_node {
    public:
        list_node (type _key, list_node *_prev, list_node *_next): key(_key), prev(_prev), next(_next) {}

        type get_key () {
            return key;
        }
        void set_key (type &_key){
            key = _key;
        }

        list_node* get_next () {
            return next;
        }
        void set_next (list_node* &_next){
            next = _next;
        }

        list_node* get_prev () {
            return prev;
        }
        void set_prev (list_node* &_prev){
            prev = _prev;
        }

    private:
        type key;
        list_node *prev, *next;
    };

    list_node *begin, *end;
};

int main()
{
    return 0;
}