????????
      +---------
FXXUF | GGFXJXLQ
       -FXXUF
        =====
        HQEUTX
       -HCFTUF
        ======
         QUCGQL
        -QQEJFC
         ======
          MQMXLQ
         -MMHUJC
          ======
          ??????

base: 12
letters: CEFGHJLMQTUX
difficulty: hard