MQW
      +---------
WWQQL | GLQXUYUF
       -QWMHWY
        ======
         FHTGTU
        -FLTTXW
         ======
          ETQTGF
         -NFTYXM
          ======
           EFHGW

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