????????
      +---------
WPWFN | XLWGXQJF
       -XYNYF
        =====
         JTRMQ
        -XYNYF
         =====
         WUHGFJ
        - LGTHW
         ======
           FRRXF
          -GYJFP
           =====
           ?????

base: 15
letters: FGHJLMNPQRTUWXY
difficulty: hard