FNPW
      +---------
HEWWN | ELRJHFFT
       -HEWWN
        =====
        TFRJNF
       -RMJWFT
        ======
         NXJREF
        -NMLWRR
         ======
           YRHLT

base: 13
letters: EFHJLMNPRTWXY
difficulty: hard
restrictions: no multiplication