????????
      +---------
YZZYR | YXJZTGVN
       -YZZYR
        =====
         TPRRG
        -PQUPT
         =====
          PZJLV
         -VMHVR
          =====
           LGZNN
          -MMTMW
           =====
           ?????

base: 16
letters: GHJLMNPQRTUVWXYZ
difficulty: hard