????????
      +---------
RJPTF | XXTLUXJY
       -RJPTF
        =====
        FNJPHX
       -FQUGQR
        ======
          YWHFJ
         -YQHMR
          =====
           YWWNY
          -YQHMR
           =====
           ?????

base: 15
letters: FGHJLMNPQRTUWXY
difficulty: hard