(VAR L N)
(RULES 
zeros -> cons(0)
U11(tt) -> tt
U21(tt) -> tt
U31(tt) -> tt
U41(tt) -> U42(isNatIList)
U42(tt) -> tt
U51(tt) -> U52(isNatList)
U52(tt) -> tt
U61(tt) -> U62(isNat)
U62(tt) -> s(length(L))
isNat -> tt
isNat -> U11(isNatList)
isNat -> U21(isNat)
isNatIList -> U31(isNatList)
isNatIList -> tt
isNatIList -> U41(isNat)
isNatList -> tt
isNatList -> U51(isNat)
length(nil) -> 0
length(cons(N)) -> U61(isNatList)
)