Admitted. (* (*N*) QuickChick trans_eq. *)
Example trans_eq_example' : forall (a b c d e f : nat),
[a;b] = [c;d] ->
[c;d] = [e;f] ->
[a;b] = [e;f].
Admitted. (* Leo: OUT-OF-SCOPE *)
Example trans_eq_exercise : forall (n m o p : nat),
m = (minustwo o) ->
(n + p) = m ->
(n + p) = (minustwo o).
Admitted. (* Leo: OUT-OF-SCOPE *)

Theorem S_injective : forall (n m : nat),
S n = S m ->
n = m.