S(S`K(S(SSS)(SSI(SS0))(S`KSK)(S`K`S(S`KS`SI)(S`K`S`KK(S`K`SI(S`KKK)))))(S`KK
(SSI`S`S`K(S`K`S`K`S(SI`K(S(SS(SSI(SS0)))(SS0)(S`KSK)))(S`K`S`KK(S`K(SS(S(SI
(SS0))(S(SSS)(SSI(SS0))))(S`KSK)(S`K`S(S`KS`SI)(S`K`S`KK(S`K`SI(S`KKK)))))(S
`K`SI(S`KKK)))))I)))I

# forward1 =
#     _1
#     [f.[r.
#         setcdr2 o-cdr2 f r r
#     ]]
# ;
# 
# [input.
#     forward1 20
#     [r.
#         y1
#         [g.[r.
#             cons2 32
#             (
#                 forward1 41
#                 [r.    
#                     o-cdr2 g r
#                 ]
#                 r
#             )
#         ]]
#         input
#     ]
#     input
# ]