∀ {G : Type u_1} {α : Type u_3} [inst : AddGroup G] [inst_1 : AddAction G α] [inst_2 : MeasurableSpace α] {s t : Set α}
  {μ : MeasureTheory.Measure α} [MeasurableConstVAdd G α] [MeasureTheory.VAddInvariantMeasure G α μ] [Countable G],
  MeasureTheory.IsAddFundamentalDomain G s μ →
    MeasureTheory.NullMeasurableSet t μ → μ s < μ t → ∃ x ∈ t, ∃ y ∈ t, ∃ g, g ≠ 0 ∧ g +ᵥ x = y