????????
      +---------
ZMHZY | ULQGVJGW
       -ZMHZY
        =====
        TNJPRJ
       -TTXVTT
        ======
         RLUXVG
        -TQWNQU
         ======
          TJULRW
         -JGWJGP
          ======
          ??????

base: 16
letters: GHJLMNPQRTUVWXYZ
difficulty: medium