???????
      +--------
PMNRL | LRCXRFY
       -PMNRL
        =====
        CMMCNF
       -CFCMUG
        ======
         FFPMFY
        -CUGFFL
         ======
         ??????

base: 12
letters: CFGJLMNPRUXY
difficulty: hard
hints: Y << J
missing: J