∀ {Γ : Type u_1} {R : Type u_3} [inst : AddCommMonoid Γ] [inst_1 : PartialOrder Γ] [inst_2 : IsOrderedCancelAddMonoid Γ]
  [inst_3 : NonAssocSemiring R] (a : R), HahnSeries.C a = (HahnSeries.single 0) a