fact: Definition RZ '(a, b) '(a', b') : Prop := (a > 0 <-> a' > 0) /\ (b > 0 <-> b' > 0).
imports: List PeanoNat Lia Relation_Operators Operators_Properties Transitive_Closure Undecidability.MinskyMachines.MM2 Undecidability.MinskyMachines.Util.MM2_facts ssreflect ssrbool ssrfun