lemma {u} ex {α : Type u} [linear_ordered_comm_ring α]
  (a_1 a_2 a_3 a_4 a_5 a_6 a_7 a_8 a_9 a_10
   a_11 a_12 a_13 a_14 a_15 a_16 a_17 a_18 a_19 a_20
   a_21 a_22 a_23 a_24 a_25 a_26 a_27 a_28 a_29 a_30 : α) :
  a_1 + a_2 + a_3 + a_4 + a_5 + a_6 + a_7 + a_8 + a_9 + a_10
+ a_11 + a_12 + a_13 + a_14 + a_15 + a_16 + a_17 + a_18 + a_19 + a_20
+ a_21 + a_22 + a_23 + a_24 + a_25 + a_26 + a_27 + a_28 + a_29 + a_30 =
  a_30 + a_29 + a_28 + a_27 + a_26 + a_25 + a_24 + a_23 + a_22 + a_21 +
  a_20 + a_19 + a_18 + a_17 + a_16 + a_15 + a_14 + a_13 + a_12 + a_11 +
  a_10 + a_9 + a_8 + a_7 + a_6 + a_5 + a_4 + a_3 + a_2 + a_1 :=
by simp
