????????
     +---------
LLNL | AEPAUNNA
      -AUULA
       =====
        AELAN
       -AUULA
        =====
         AALLN
        - LLNL
         =====
          EPPAA
         -EUUPP
          =====
          ?????

base: 7
letters: AELNPUY
missing: Y
difficulty: intermediate