(*s The length of a path without repetition is less than the cardinal of the map representing the graph *)

Lemma CG_path_app_2 :
forall (l1 l2 : list ad) (last x : ad) (d : D),
CG_path last d (l1 ++ x :: l2) -> {d2 : D &  CG_path last d2 (x :: l2)}.