????????
      +---------
FLUJP | GQPUHFQP
       -RQQNM
        =====
        FTFFFF
       - MHRLL
        ======
         FFJMHQ
        -FFGRJN
         ======
           UPLLP
          -NHPFF
           =====
           ?????

base: 13
letters: FGHJLMNPQRTUW
difficulty: intermediate
missing: W