UFHL
      +---------
RFQHH | XWTTNXPN
       -RFQHH
        =====
        JUMWRX
       -JGXFHU
        ======
         UHHPWP
        -UGHMJJ
         ======
          UQRYUN
         -URXTYY
          ======
           YWFWL

base: 15
letters: FGHJLMNPQRTUWXY
difficulty: hard
missing: L