Section INVARIANT1.
Remark add_reduce1 :
forall x1 x2 y : Z, x1 = x2 -> (y + x1 - 1)%Z = (y + x2 - 1)%Z.

Lemma invariant1 :
forall c : Config,
legal c ->
sigma_send_table (st c) =
(sigma_receive_table (rt c) + sigma_weight (bm c) - 1)%Z.