∀ {α : Type u_1} {M : Type u_3} [inst : AddCommMonoid M] {f : α → M} [inst_1 : AddCommMonoid α]
  [inst_2 : PartialOrder α] [IsOrderedCancelAddMonoid α] [ExistsAddOfLE α] [inst_5 : LocallyFiniteOrder α]
  [inst_6 : Sub α] [OrderedSub α] (a b c : α), ∑ x ∈ Finset.Ico (a + c) (b + c), f (x - c) = ∑ x ∈ Finset.Ico a b, f x