(VAR X XS N X1 X2)
(RULES 
a__from(X) -> cons(mark(X),from(s(X)))
a__head(cons(X,XS)) -> mark(X)
a__2nd(cons(X,XS)) -> a__head(mark(XS))
a__take(0,XS) -> nil
a__take(s(N),cons(X,XS)) -> cons(mark(X),take(N,XS))
a__sel(0,cons(X,XS)) -> mark(X)
a__sel(s(N),cons(X,XS)) -> a__sel(mark(N),mark(XS))
mark(from(X)) -> a__from(mark(X))
mark(head(X)) -> a__head(mark(X))
mark(2nd(X)) -> a__2nd(mark(X))
mark(take(X1,X2)) -> a__take(mark(X1),mark(X2))
mark(sel(X1,X2)) -> a__sel(mark(X1),mark(X2))
mark(cons(X1,X2)) -> cons(mark(X1),X2)
mark(s(X)) -> s(mark(X))
mark(0) -> 0
mark(nil) -> nil
a__from(X) -> from(X)
a__head(X) -> head(X)
a__2nd(X) -> 2nd(X)
a__take(X1,X2) -> take(X1,X2)
a__sel(X1,X2) -> sel(X1,X2)
)