????????
      +---------
HUWXH | TRUZGTMH
       -MRLTV
        =====
         XPNRT
        -XTRUG
         =====
          ZRWNM
         -LNQNL
          =====
           TVYLH
          -MRLTV
           =====
           ?????

base: 16
letters: GHJLMNPQRTUVWXYZ
difficulty: hard
missing: J