Let x0 of type ο be given.
Apply H0 with
λ x1 . pack_u (setprod omega x1) (λ x2 . lam 2 (λ x3 . If_i (x3 = 0) (ordsucc (ap x2 0)) (ap x2 1))).
Let x1 of type ο be given.
Apply H1 with
λ x2 x3 x4 . lam (setprod omega x2) (λ x5 . lam 2 (λ x6 . If_i (x6 = 0) (ap x5 0) (ap x4 (ap x5 1)))).
Let x2 of type ο be given.
Apply H2 with
λ x3 . lam x3 (λ x4 . lam 2 (λ x5 . If_i (x5 = 0) 0 x4)).
Let x3 of type ο be given.