NXGP
      +---------
ZRRZQ | WXUTXWXN
       -ZRRZQ
        =====
        NZXRUW
       -NYRHZL
        ======
         ZZNPJX
        -ZYMTRM
         ======
          NXNYLN
         -NHVGTW
          ======
           ZNZHG

base: 16
letters: GHJLMNPQRTUVWXYZ
difficulty: medium