????????
      +---------
WUZVR | QYUWUJXV
       -WUZVR
        =====
         UJQPJ
        -HHWXV
         =====
         WMGVWX
        -WHVTGJ
         ======
          LLZWPV
         -LJNZYH
          ======
          ??????

base: 16
letters: GHJLMNPQRTUVWXYZ
difficulty: medium