????????
      +---------
LMRYU | TTZZXTPH
       -WVNYQ
        =====
        XHTGXT
       -XHGVTQ
        ======
          ZNUTP
         -LMRYU
          =====
           VVTNH
          -VNJHU
           =====
           ?????

base: 16
letters: GHJLMNPQRTUVWXYZ
difficulty: hard