(\lambda (x0: T).(\lambda (x1: T).(\lambda (H2: (eq T t5 (THead k x0
x1))).(eq_ind_r T (THead k x0 x1) (\lambda (t: T).(iso (THead k v1 t3) t))
(iso_head v1 x0 t3 x1 k) t5 H2)))) H1)))))))))) t1 t2 H))).
(\lambda (x0: T).(\lambda (x1: T).(\lambda (H2: (eq T t5 (THead k x0
x1))).(eq_ind_r T (THead k x0 x1) (\lambda (t: T).(iso (THead k v1 t3) t))
(iso_head v1 x0 t3 x1 k) t5 H2)))) H1)))))))))) t1 t2 H))).