(VAR X X1 X2 X3 Y Z )
(RULES 
        active(primes) -> mark(sieve(from(s(s(0)))))
        active(from(X)) -> mark(cons(X, from(s(X))))
        active(head(cons(X, Y))) -> mark(X)
        active(tail(cons(X, Y))) -> mark(Y)
        active(if(true, X, Y)) -> mark(X)
        active(if(false, X, Y)) -> mark(Y)
        active(filter(s(s(X)), cons(Y, Z))) -> mark(if(divides(s(s(X)), Y), filter(s(s(X)), Z), cons(Y, filter(X, sieve(Y)))))
        active(sieve(cons(X, Y))) -> mark(cons(X, filter(X, sieve(Y))))
        mark(primes) -> active(primes)
        mark(sieve(X)) -> active(sieve(mark(X)))
        mark(from(X)) -> active(from(mark(X)))
        mark(s(X)) -> active(s(mark(X)))
        mark(0) -> active(0)
        mark(cons(X1, X2)) -> active(cons(mark(X1), X2))
        mark(head(X)) -> active(head(mark(X)))
        mark(tail(X)) -> active(tail(mark(X)))
        mark(if(X1, X2, X3)) -> active(if(mark(X1), X2, X3))
        mark(true) -> active(true)
        mark(false) -> active(false)
        mark(filter(X1, X2)) -> active(filter(mark(X1), mark(X2)))
        mark(divides(X1, X2)) -> active(divides(mark(X1), mark(X2)))
        sieve(mark(X)) -> sieve(X)
        sieve(active(X)) -> sieve(X)
        from(mark(X)) -> from(X)
        from(active(X)) -> from(X)
        s(mark(X)) -> s(X)
        s(active(X)) -> s(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)
        head(mark(X)) -> head(X)
        head(active(X)) -> head(X)
        tail(mark(X)) -> tail(X)
        tail(active(X)) -> tail(X)
        if(mark(X1), X2, X3) -> if(X1, X2, X3)
        if(X1, mark(X2), X3) -> if(X1, X2, X3)
        if(X1, X2, mark(X3)) -> if(X1, X2, X3)
        if(active(X1), X2, X3) -> if(X1, X2, X3)
        if(X1, active(X2), X3) -> if(X1, X2, X3)
        if(X1, X2, active(X3)) -> if(X1, X2, X3)
        filter(mark(X1), X2) -> filter(X1, X2)
        filter(X1, mark(X2)) -> filter(X1, X2)
        filter(active(X1), X2) -> filter(X1, X2)
        filter(X1, active(X2)) -> filter(X1, X2)
        divides(mark(X1), X2) -> divides(X1, X2)
        divides(X1, mark(X2)) -> divides(X1, X2)
        divides(active(X1), X2) -> divides(X1, X2)
        divides(X1, active(X2)) -> divides(X1, X2)
        
)