(VAR X Y Z X1 X2)
(RULES 
active(2nd(cons(X,cons(Y,Z)))) -> mark(Y)
active(from(X)) -> mark(cons(X,from(s(X))))
mark(2nd(X)) -> active(2nd(mark(X)))
mark(cons(X1,X2)) -> active(cons(mark(X1),X2))
mark(from(X)) -> active(from(mark(X)))
mark(s(X)) -> active(s(mark(X)))
2nd(mark(X)) -> 2nd(X)
2nd(active(X)) -> 2nd(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)
from(mark(X)) -> from(X)
from(active(X)) -> from(X)
s(mark(X)) -> s(X)
s(active(X)) -> s(X)
)