LMW
      +---------
RLRMF | YFXGPQRY
       -YJPGXX
        ======
         GMTYMR
        -GRMWNW
         ======
          RYJYQY
         -GMJRXQ
          ======
           JWXPX

base: 13
letters: FGJLMNPQRTWXY
difficulty: medium
restrictions: no multiplication