proposition: Lemma ltn_simpl2 n n' n'': (n * n' + n + n' < n * n'' + n + n'') = (n' < n'').
proof: Proof. by rewrite addnAC (addnAC _ _ n'') ltn_add2r - ! mulSnr ltn_mul2l. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(fintype bigop)