text: #ifndef LISTS
  #define LISTS
  #include <stdlib.h>
  #include <string.h>
  #include <stdio.h>
  
  /**
   * struct dlistint_s - doubly linked list
   * @n: integer
   * @prev: points to the previous node
   * @next: points to the next node
   *
   * Description: doubly linked list node structure
   * for Holberton project
   */
  typedef struct dlistint_s
  {
      int n;
      struct dlistint_s *prev;
      struct dlistint_s *next;
  } dlistint_t;
  
  size_t print_dlistint(const dlistint_t *h);
  size_t dlistint_len(const dlistint_t *h);
  dlistint_t *add_dnodeint(dlistint_t **head, const int n);
  dlistint_t *add_dnodeint_end(dlistint_t **head, const int n);
  void free_dlistint(dlistint_t *head);
  dlistint_t *get_dnodeint_at_index(dlistint_t *head, unsigned int index);
  int sum_dlistint(dlistint_t *head);
  dlistint_t *insert_dnodeint_at_index(dlistint_t **h, unsigned int idx, int n);
  int delete_dnodeint_at_index(dlistint_t **head, unsigned int index);
  
  #endif