????????
      +---------
NJUPY | RRJXRLYG
       -UGQFL
        =====
        NYTYHL
       -NQPPJH
        ======
         NYPYHY
        -NQPPJH
         ======
          NFPYXG
         - HRWXT
          ======
          ??????

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