- ∀L. ⇩[0, e] L @@ L1 ≡ L @@ L2.
-#L1 #L2 #d #e #H elim H -L1 -L2 -d -e normalize
-/4 width=1 by ldrop_skip_lt, ldrop_ldrop, arith_b1, lt_minus_to_plus_r, monotonic_pred/
+ ∀L. ⇩[s, 0, e] L @@ L1 ≡ L @@ L2.
+#L1 #L2 #s #d #e #H elim H -L1 -L2 -d -e normalize
+[2,3,4: /4 width=1 by ldrop_skip_lt, ldrop_drop, arith_b1, lt_minus_to_plus_r, monotonic_pred/ ]
+#d #e #_ #_ #H <(le_n_O_to_eq … H) -H //