(VAR X Y Z I P X1 X2) (RULES active(__(__(X,Y),Z)) -> mark(__(X,__(Y,Z))) active(__(X,nil)) -> mark(X) active(__(nil,X)) -> mark(X) active(U11(tt)) -> mark(U12(tt)) active(U12(tt)) -> mark(tt) active(isNePal(__(I,__(P,I)))) -> mark(U11(tt)) active(__(X1,X2)) -> __(active(X1),X2) active(__(X1,X2)) -> __(X1,active(X2)) active(U11(X)) -> U11(active(X)) active(U12(X)) -> U12(active(X)) active(isNePal(X)) -> isNePal(active(X)) __(mark(X1),X2) -> mark(__(X1,X2)) __(X1,mark(X2)) -> mark(__(X1,X2)) U11(mark(X)) -> mark(U11(X)) U12(mark(X)) -> mark(U12(X)) isNePal(mark(X)) -> mark(isNePal(X)) proper(__(X1,X2)) -> __(proper(X1),proper(X2)) proper(nil) -> ok(nil) proper(U11(X)) -> U11(proper(X)) proper(tt) -> ok(tt) proper(U12(X)) -> U12(proper(X)) proper(isNePal(X)) -> isNePal(proper(X)) __(ok(X1),ok(X2)) -> ok(__(X1,X2)) U11(ok(X)) -> ok(U11(X)) U12(ok(X)) -> ok(U12(X)) isNePal(ok(X)) -> ok(isNePal(X)) top(mark(X)) -> top(proper(X)) top(ok(X)) -> top(active(X)) )