fact: Definition Double2 (n : nat) : nat := S (S (Double n)).
imports: HoTT.Spaces.Nat HoTT.Tactics HoTT.Classes.interfaces.abstract_algebra HoTT.Classes.interfaces.naturals HoTT.Classes.interfaces.orders HoTT.Classes.implementations.peano_naturals HoTT.Classes.theory.rings HoTT.Classes.orders.semirings HoTT.Classes.theory.apartness