????????
      +---------
UXHFH | UHFHGNUU
       -UXHFH
        =====
         GQPFN
        -GMLJJ
         =====
          QXLGU
         -UXHFH
          =====
           EWLLU
          -EFEUJ
           =====
           ?????

base: 14
letters: EFGHJLMNPQUWXY
difficulty: medium
missing: Y