????????
      +---------
LPYTT | UPPFTMFP
       -EFMXL
        =====
        MLXULM
       -MMUTQJ
        ======
         QPQQMF
        -QFELLJ
         ======
          FLEEFP
         -FMJXEL
          ======
          ??????

base: 12
letters: CEFJLMPQTUXY
missing: C
difficulty: hard