QXJ
      +--------
WTJLX | NGNPWPQ
       -WTJLX
        =====
        LQULMP
       -FRNFRF
        ======
         XFHWYQ
        -XULLHM
         ======
           PFLN

base: 15
letters: FGHJLMNPQRTUWXY
difficulty: medium