proposition: Fact pair_one_neq0 : (1, 1) != 0 :> R1 * R2.
proof: Proof. by rewrite xpair_eqE oner_eq0. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)