(VAR X Z Y X1 X2)
(RULES 
from(X) -> cons(X,n__from(n__s(X)))
first(0,Z) -> nil
first(s(X),cons(Y,Z)) -> cons(Y,n__first(X,activate(Z)))
sel(0,cons(X,Z)) -> X
sel(s(X),cons(Y,Z)) -> sel(X,activate(Z))
from(X) -> n__from(X)
s(X) -> n__s(X)
first(X1,X2) -> n__first(X1,X2)
activate(n__from(X)) -> from(activate(X))
activate(n__s(X)) -> s(activate(X))
activate(n__first(X1,X2)) -> first(activate(X1),activate(X2))
activate(X) -> X
)