(VAR I P X X1 X2 Y Z )
(RULES 
        active(__(__(X, Y), Z)) -> mark(__(X, __(Y, Z)))
        active(__(X, nil)) -> mark(X)
        active(__(nil, X)) -> mark(X)
        active(and(tt, X)) -> mark(X)
        active(isNePal(__(I, __(P, I)))) -> mark(tt)
        mark(__(X1, X2)) -> active(__(mark(X1), mark(X2)))
        mark(nil) -> active(nil)
        mark(and(X1, X2)) -> active(and(mark(X1), X2))
        mark(tt) -> active(tt)
        mark(isNePal(X)) -> active(isNePal(mark(X)))
        __(mark(X1), X2) -> __(X1, X2)
        __(X1, mark(X2)) -> __(X1, X2)
        __(active(X1), X2) -> __(X1, X2)
        __(X1, active(X2)) -> __(X1, X2)
        and(mark(X1), X2) -> and(X1, X2)
        and(X1, mark(X2)) -> and(X1, X2)
        and(active(X1), X2) -> and(X1, X2)
        and(X1, active(X2)) -> and(X1, X2)
        isNePal(mark(X)) -> isNePal(X)
        isNePal(active(X)) -> isNePal(X)
        
)