????????
      +---------
QYWHP | JXLMXNXM
       -QYWHP
        =====
        QQXHVN
       -TGVVHY
        ======
         QHJPJX
        -QQMQMQ
         ======
           YUZYM
          -JZRLV
           =====
           ?????

base: 16
letters: GHJLMNPQRTUVWXYZ
difficulty: medium