????????
      +---------
NPYFY | RYGRFNXP
       -NPYFY
        =====
        YJWNYN
       -YFGTJT
        ======
         TGYPFX
        -TMLQXP
         ======
          XTWLPP
         -XUJLJQ
          ======
          ??????

base: 14
letters: FGJLMNPQRTUWXY
difficulty: medium