(VAR X N M X1 X2)
(RULES 
active(and(tt,X)) -> mark(X)
active(plus(N,0)) -> mark(N)
active(plus(N,s(M))) -> mark(s(plus(N,M)))
active(and(X1,X2)) -> and(active(X1),X2)
active(plus(X1,X2)) -> plus(active(X1),X2)
active(plus(X1,X2)) -> plus(X1,active(X2))
active(s(X)) -> s(active(X))
and(mark(X1),X2) -> mark(and(X1,X2))
plus(mark(X1),X2) -> mark(plus(X1,X2))
plus(X1,mark(X2)) -> mark(plus(X1,X2))
s(mark(X)) -> mark(s(X))
proper(and(X1,X2)) -> and(proper(X1),proper(X2))
proper(tt) -> ok(tt)
proper(plus(X1,X2)) -> plus(proper(X1),proper(X2))
proper(0) -> ok(0)
proper(s(X)) -> s(proper(X))
and(ok(X1),ok(X2)) -> ok(and(X1,X2))
plus(ok(X1),ok(X2)) -> ok(plus(X1,X2))
s(ok(X)) -> ok(s(X))
top(mark(X)) -> top(proper(X))
top(ok(X)) -> top(active(X))
)