????????
      +---------
MUTUP | JTNNTQWQ
       -HWPWJ
        =====
        MVZQVQ
       -MNLQHZ
        ======
         NHTWMW
        -NUYJYQ
         ======
          VNPGUQ
         -VXNLXR
          ======
          ??????

base: 16
letters: GHJLMNPQRTUVWXYZ
difficulty: medium