(VAR N XS YS X ZS X1 X2 X3 X4)
(RULES 
active(natsFrom(N)) -> mark(cons(N,natsFrom(s(N))))
active(fst(pair(XS,YS))) -> mark(XS)
active(snd(pair(XS,YS))) -> mark(YS)
active(splitAt(0,XS)) -> mark(pair(nil,XS))
active(splitAt(s(N),cons(X,XS))) -> mark(u(splitAt(N,XS),N,X,XS))
active(u(pair(YS,ZS),N,X,XS)) -> mark(pair(cons(X,YS),ZS))
active(head(cons(N,XS))) -> mark(N)
active(tail(cons(N,XS))) -> mark(XS)
active(sel(N,XS)) -> mark(head(afterNth(N,XS)))
active(take(N,XS)) -> mark(fst(splitAt(N,XS)))
active(afterNth(N,XS)) -> mark(snd(splitAt(N,XS)))
mark(natsFrom(X)) -> active(natsFrom(mark(X)))
mark(cons(X1,X2)) -> active(cons(mark(X1),X2))
mark(s(X)) -> active(s(mark(X)))
mark(fst(X)) -> active(fst(mark(X)))
mark(pair(X1,X2)) -> active(pair(mark(X1),mark(X2)))
mark(snd(X)) -> active(snd(mark(X)))
mark(splitAt(X1,X2)) -> active(splitAt(mark(X1),mark(X2)))
mark(0) -> active(0)
mark(nil) -> active(nil)
mark(u(X1,X2,X3,X4)) -> active(u(mark(X1),X2,X3,X4))
mark(head(X)) -> active(head(mark(X)))
mark(tail(X)) -> active(tail(mark(X)))
mark(sel(X1,X2)) -> active(sel(mark(X1),mark(X2)))
mark(afterNth(X1,X2)) -> active(afterNth(mark(X1),mark(X2)))
mark(take(X1,X2)) -> active(take(mark(X1),mark(X2)))
natsFrom(mark(X)) -> natsFrom(X)
natsFrom(active(X)) -> natsFrom(X)
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)
s(mark(X)) -> s(X)
s(active(X)) -> s(X)
fst(mark(X)) -> fst(X)
fst(active(X)) -> fst(X)
pair(mark(X1),X2) -> pair(X1,X2)
pair(X1,mark(X2)) -> pair(X1,X2)
pair(active(X1),X2) -> pair(X1,X2)
pair(X1,active(X2)) -> pair(X1,X2)
snd(mark(X)) -> snd(X)
snd(active(X)) -> snd(X)
splitAt(mark(X1),X2) -> splitAt(X1,X2)
splitAt(X1,mark(X2)) -> splitAt(X1,X2)
splitAt(active(X1),X2) -> splitAt(X1,X2)
splitAt(X1,active(X2)) -> splitAt(X1,X2)
u(mark(X1),X2,X3,X4) -> u(X1,X2,X3,X4)
u(X1,mark(X2),X3,X4) -> u(X1,X2,X3,X4)
u(X1,X2,mark(X3),X4) -> u(X1,X2,X3,X4)
u(X1,X2,X3,mark(X4)) -> u(X1,X2,X3,X4)
u(active(X1),X2,X3,X4) -> u(X1,X2,X3,X4)
u(X1,active(X2),X3,X4) -> u(X1,X2,X3,X4)
u(X1,X2,active(X3),X4) -> u(X1,X2,X3,X4)
u(X1,X2,X3,active(X4)) -> u(X1,X2,X3,X4)
head(mark(X)) -> head(X)
head(active(X)) -> head(X)
tail(mark(X)) -> tail(X)
tail(active(X)) -> tail(X)
sel(mark(X1),X2) -> sel(X1,X2)
sel(X1,mark(X2)) -> sel(X1,X2)
sel(active(X1),X2) -> sel(X1,X2)
sel(X1,active(X2)) -> sel(X1,X2)
afterNth(mark(X1),X2) -> afterNth(X1,X2)
afterNth(X1,mark(X2)) -> afterNth(X1,X2)
afterNth(active(X1),X2) -> afterNth(X1,X2)
afterNth(X1,active(X2)) -> afterNth(X1,X2)
take(mark(X1),X2) -> take(X1,X2)
take(X1,mark(X2)) -> take(X1,X2)
take(active(X1),X2) -> take(X1,X2)
take(X1,active(X2)) -> take(X1,X2)
)