∃∃I,K. |K| = n & L = K. ⓘ{I}.
#n *
[ >length_atom #H destruct
∃∃I,K. |K| = n & L = K. ⓘ{I}.
#n *
[ >length_atom #H destruct
∃∃I,K. n = |K| & L = K. ⓘ{I}.
#n #L #H lapply (sym_eq ??? H) -H
#H elim (length_inv_succ_dx … H) -H /2 width=4 by ex2_2_intro/
∃∃I,K. n = |K| & L = K. ⓘ{I}.
#n #L #H lapply (sym_eq ??? H) -H
#H elim (length_inv_succ_dx … H) -H /2 width=4 by ex2_2_intro/