(VAR w x y z )
(RULES 
        app(app(lt,app(s,x)),app(s,y)) -> app(app(lt,x),y)
        app(app(lt,0),app(s,y)) -> true
        app(app(lt,y),0) -> false
        app(app(eq,x),x) -> true
        app(app(eq,app(s,x)),0) -> false
        app(app(eq,0),app(s,x)) -> false
        app(app(member,w),null) -> false
        app(app(member,w),app(app(app(fork,x),y),z)) -> app(app(app(if,app(app(lt,w),y)),app(app(member,w),x)),app(app(app(if,app(app(eq,w),y)),true),app(app(member,w),z)))
        
)