????????
      +---------
NRXYY | QMNNTNGJ
       -LFFTH
        =====
        NWHFWN
       -WTTMYW
        ======
         WHPLWG
        -WPLQTL
         ======
          WNPWPJ
         -WWWTYR
          ======
          ??????

base: 15
letters: FGHJLMNPQRTUWXY
difficulty: hard
hints: M << J
missing: U