UJQ
      +--------
NYQMR | PNGWWRJ
       -JRJXR
        =====
         LQWHR
        -HYNYX
         =====
         NUTNRJ
        -NUNGNX
         ======
           MTUJ

base: 15
letters: FGHJLMNPQRTUWXY
difficulty: challenging
hints: G << P, N << F
missing: F