∀ {Γ : Type u_1} {R : Type u_3} [inst : AddCommMonoid Γ] [inst_1 : LinearOrder Γ] [inst_2 : IsOrderedCancelAddMonoid Γ]
  [inst_3 : NonUnitalNonAssocSemiring R] (x y : HahnSeries Γ R) [NoZeroDivisors R],
  (x * y).orderTop = x.orderTop + y.orderTop