MQR
      +---------
TRXRT | QPTMHGGM
       -GMTWQJ
        ======
         RHHGXG
        -RWWETM
         ======
          EEREMM
         -FXXJWX
          ======
           RYJXX

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