proposition: Lemma natsum_of_intK : cancel natsum_of_int int_of_natsum.
proof: Proof. by case. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(fintype finfun bigop order ssralg countalg ssrnum) mathcomp(poly)