????????
      +---------
JFNUH | WGRNHWYR
       -JFNUH
        =====
        QYLWMW
       -QQLFTP
        ======
         GMMJJY
        -PXGJLJ
         ======
          THMUHR
         -TUMLFQ
          ======
          ??????

base: 15
letters: FGHJLMNPQRTUWXY
difficulty: hard
hints: R < L, U << R