(VAR L X V1 V V2 N X1 X2)
(RULES 
active(zeros) -> mark(cons(0,zeros))
active(U11(tt,L)) -> mark(s(length(L)))
active(and(tt,X)) -> mark(X)
active(isNat(0)) -> mark(tt)
active(isNat(length(V1))) -> mark(isNatList(V1))
active(isNat(s(V1))) -> mark(isNat(V1))
active(isNatIList(V)) -> mark(isNatList(V))
active(isNatIList(zeros)) -> mark(tt)
active(isNatIList(cons(V1,V2))) -> mark(and(isNat(V1),isNatIList(V2)))
active(isNatList(nil)) -> mark(tt)
active(isNatList(cons(V1,V2))) -> mark(and(isNat(V1),isNatList(V2)))
active(length(nil)) -> mark(0)
active(length(cons(N,L))) -> mark(U11(and(isNatList(L),isNat(N)),L))
mark(zeros) -> active(zeros)
mark(cons(X1,X2)) -> active(cons(mark(X1),X2))
mark(0) -> active(0)
mark(U11(X1,X2)) -> active(U11(mark(X1),X2))
mark(tt) -> active(tt)
mark(s(X)) -> active(s(mark(X)))
mark(length(X)) -> active(length(mark(X)))
mark(and(X1,X2)) -> active(and(mark(X1),X2))
mark(isNat(X)) -> active(isNat(X))
mark(isNatList(X)) -> active(isNatList(X))
mark(isNatIList(X)) -> active(isNatIList(X))
mark(nil) -> active(nil)
cons(mark(X1),X2) -> cons(X1,X2)
cons(X1,mark(X2)) -> cons(X1,X2)
cons(active(X1),X2) -> cons(X1,X2)
cons(X1,active(X2)) -> cons(X1,X2)
U11(mark(X1),X2) -> U11(X1,X2)
U11(X1,mark(X2)) -> U11(X1,X2)
U11(active(X1),X2) -> U11(X1,X2)
U11(X1,active(X2)) -> U11(X1,X2)
s(mark(X)) -> s(X)
s(active(X)) -> s(X)
length(mark(X)) -> length(X)
length(active(X)) -> length(X)
and(mark(X1),X2) -> and(X1,X2)
and(X1,mark(X2)) -> and(X1,X2)
and(active(X1),X2) -> and(X1,X2)
and(X1,active(X2)) -> and(X1,X2)
isNat(mark(X)) -> isNat(X)
isNat(active(X)) -> isNat(X)
isNatList(mark(X)) -> isNatList(X)
isNatList(active(X)) -> isNatList(X)
isNatIList(mark(X)) -> isNatIList(X)
isNatIList(active(X)) -> isNatIList(X)
)