????????
      +---------
NQRLF | TGRQLPGJ
       -NQRLF
        =====
        MEUMQP
       -MUWTJP
        ======
         PQPMUG
        -PUJFGN
         ======
          NQPTLJ
         -NGMJWW
          ======
          ??????

base: 13
letters: EFGJLMNPQRTUW
difficulty: hard