RNTP
      +---------
NPMMN | XRWTUMNQ
       -MLRYM
        =====
        YNTNQM
       -YRUNQY
        ======
         YJHHWN
        -YWRGUT
         ======
          YGRXFQ
         -YUJPNJ
          ======
            MNJJ

base: 15
letters: FGHJLMNPQRTUWXY
difficulty: hard