Red Beard sees an old ship on the sea. People say there is a treasure map on it! But Red Beard only finds seven wood bricks (木块) there. “The map might be inside one of the bricks!” Red Beard thinks. Maybe someone hollowed out (挖空) a brick and put the map inside. That brick should be lighter than the others. Red Beard has a scale (天平) to weigh the bricks. But he can only use it twice. Can you help him find the map?