∀ (α : Type u_1) (β : Type u_2) [inst : AddMonoid α] [inst_1 : PartialOrder α] [inst_2 : AddMonoid β]
  [inst_3 : Preorder β] (m : α) (n : β), (OrderAddMonoidHom.inl α β) m + (OrderAddMonoidHom.inr α β) n = (m, n)