DOUBLE_MIDDLE

void mid_elem(node_t *list)
{
    node_t *fwd = list;
    node_t *back = list -> prev;
    while(fwd != back && fwd->next != back)
    {
        fwd = fwd->next;
        back=back->prev;
    }

    printf("MIDDLE IS %d", fwd->data);
}