fact: Definition f1 : forall x, (forall z, lte z x -> {y:nat | odd z \/ y <= (z./2).-1}) -> {y:nat | odd x \/ y <= (x./2).-1}.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(fintype bigop)