node *insert(node *head)
{
    node *find(node *p, int a);
    node *new;           /* pointer to new node */

    node *n1;        /* pointer to node preceding key node */
int key;
    int x;            /* new item (number) to be inserted */


    printf(“Value of new item?”);
    scanf(“%d”, &x);
    printf(“Value of key item ? (type –999 if last) “);
    scanf(“%d”, &key);

    if(head->number == key)         /* new node is first */

    {
    new = (node *)malloc(size of(node));
    new ->number = x;
    new->next = head;
    head = new;
    }
    else/* find key node and insert new node */

    {            /* before the key node */

        n1 = find(head, key);    /* find key node */
if(n1 == NULL)
           printf(“\n key is not found \n”);
        else/* insert new node */

        {
    new = (node *)malloc(sizeof(node));
    new->number = x;
    new->next = n1->next;
    n1->next = new;
        }
      }
return(head);
}
node *find(node *lists, int key)
{
        if(list->next->number == key)      /* key found */
return(list);
    elseif(list->next->next == NULL)     /* end */
return(NULL);
    else
        find(list->next, key);
}