????????
      +---------
RCMXR | PXPXWXCC
       -RCMXR
        =====
         CQXEX
        -CCXXM
         =====
          CXCWC
         -PQWXP
          =====
          RXHWPC
         - QQXXW
          ======
          ??????

base: 9
letters: CEHMPQRWX
difficulty: medium