class node {
public:
  int data;
  node *next;
  node *prev;
  node(int d) {
    this->data = d;
    this->next = NULL;
    this->prev = NULL;
  }
  ~node() {
    int value = this -> data;
    if (next != NULL) {
      delete next;
      next = NULL;
    }
    cout << "memory free for node with data " << value << endl;
  }
};