#include <iostream>
#include<math.h>
using namespace std;
class List {
public:
    int number;
};

class OBJ {
public:
    List b;
    class OBJ* prev, * next;
};
OBJ* head = NULL; OBJ* tail = NULL;
void add_obj(OBJ* obj, List list) {
    OBJ* ptr = new OBJ;
    ptr->b = list;
    ptr->prev = obj;
    ptr->next = (obj == NULL) ? NULL : obj->next;
    if (obj != NULL) {
        obj->next = ptr;
        if (obj->next != NULL) obj->next->prev = ptr;
    }
    if (ptr->prev == NULL) head = ptr;
    if (ptr->next == NULL) tail = ptr;
}
void show() {
    OBJ* c = head;
    while (c != NULL) {
        cout << c->b.number << endl;
        c = c->next;
    }
}
void reverse(OBJ*& head)
{
    OBJ* pred = NULL;
    OBJ* current = head;
    while (current != NULL)
    {
        OBJ* next2 = current->next;
        current->next = pred;
        pred = current;
        current = next2;
    }

    head = pred;
}

int main() {
    int N = 6;
    setlocale(LC_ALL, "rus");
    List a = { 0 };
    add_obj(tail, a);
    for (int i = 1; i < N; i++) {
        a.number = i;
        add_obj(tail, a);
    }
    show();
    reverse(head);
    show ();
    return 0;
}