PNFU
      +---------
HEJQE | XHYWMXWM
       -GUJPM
        =====
        HGYEWX
       -HPYMUU
        ======
         HWHPNW
        - EFUNH
         ======
          HQYJJM
         -HFPMWF
          ======
           HPGJG

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