????????
      +---------
JXHJP | RWLQYHXT
       -JXHJP
        =====
        TUNXVH
       - JXHJP
        ======
         PXTNUX
        -PTXYVR
         ======
          QQJULT
         -GWWGMH
          ======
          ??????

base: 16
letters: GHJLMNPQRTUVWXYZ
difficulty: medium
missing: Z