X na

X naX naX naX naX naX na
X naX naX naX naX naX na
X naX naX naX naX naX naX naX naX naX naX naX naX naX naX naX naX naX naX naX naX naX naX naX naX naX naX naX naX naX naX naX naX naX naX naX na