(VAR L N V V1 V2 X X1 X2 )
(RULES 
        zeros -> cons(0, n__zeros)
        U11(tt) -> tt
        U21(tt) -> tt
        U31(tt) -> tt
        U41(tt, V2) -> U42(isNatIList(activate(V2)))
        U42(tt) -> tt
        U51(tt, V2) -> U52(isNatList(activate(V2)))
        U52(tt) -> tt
        U61(tt, L, N) -> U62(isNat(activate(N)), activate(L))
        U62(tt, L) -> s(length(activate(L)))
        isNat(n__0) -> tt
        isNat(n__length(V1)) -> U11(isNatList(activate(V1)))
        isNat(n__s(V1)) -> U21(isNat(activate(V1)))
        isNatIList(V) -> U31(isNatList(activate(V)))
        isNatIList(n__zeros) -> tt
        isNatIList(n__cons(V1, V2)) -> U41(isNat(activate(V1)), activate(V2))
        isNatList(n__nil) -> tt
        isNatList(n__cons(V1, V2)) -> U51(isNat(activate(V1)), activate(V2))
        length(nil) -> 0
        length(cons(N, L)) -> U61(isNatList(activate(L)), activate(L), N)
        zeros -> n__zeros
        0 -> n__0
        length(X) -> n__length(X)
        s(X) -> n__s(X)
        cons(X1, X2) -> n__cons(X1, X2)
        nil -> n__nil
        activate(n__zeros) -> zeros
        activate(n__0) -> 0
        activate(n__length(X)) -> length(X)
        activate(n__s(X)) -> s(X)
        activate(n__cons(X1, X2)) -> cons(X1, X2)
        activate(n__nil) -> nil
        activate(X) -> X
        
)