????????
      +---------
NTHTX | YYUTZTMW
       -NTHTX
        =====
        VLWJPT
       -VRTXQN
        ======
         NLVULM
        -NWYMZN
         ======
           GMZVW
          -WXZZY
           =====
           ?????

base: 16
letters: GHJLMNPQRTUVWXYZ
difficulty: medium