JQN
      +---------
EPQXF | FREHXWMH
       -FJRJNW
        ======
         QRJGLM
        - EPQXF
         ======
          GMRPFH
         -MNEHJP
          ======
           ENQPP

base: 13
letters: EFGHJLMNPQRWX
difficulty: intermediate
restrictions: no multiplication