proposition: Lemma ex_euclid_cont (tr0 : t < size r0) : exists k, euclid_cont k.
proof: Proof. exists O; apply/forallP => /= j. by move: (ltn_ord j); rewrite ltnS leqn0 => /eqP ->. Qed.
imports: mathcomp(all_ssreflect ssralg poly polydiv matrix)