????????
      +---------
PQNCC | UQQMCJMQ
       -YMJWP
        =====
        JPWUPJ
       -JJUCGL
        ======
         GQGGJM
        -GMYPPL
         ======
          MPYYMQ
         -MJLWYP
          ======
          ??????

base: 12
letters: CGJLMNPQRUWY
missing: R
difficulty: hard