????????
      +---------
ZQZHH | PHPUXLXU
       -UHTZN
        =====
        ZNXWXL
       - RPJYN
        ======
         ZJLZLX
        -ZGUZMP
         ======
          ZTNNMU
         -ZXVQRL
          ======
          ??????

base: 16
letters: GHJLMNPQRTUVWXYZ
difficulty: medium