qed.
lemma sex_length_isid: ∀R,L1,L2. |L1| = |L2| →
- â\88\80f. ð\9d\90\88â\9dªfâ\9d« → L1 ⪤[R,cfull,f] L2.
+ â\88\80f. ð\9d\90\88â\9d¨fâ\9d© → L1 ⪤[R,cfull,f] L2.
#R #L1 elim L1 -L1
[ #Y2 #H >(length_inv_zero_sn … H) -Y2 //
| #L1 #I1 #IH #Y2 #H #f #Hf