GQMQ
      +---------
YQPLX | JHYPYPYJ
       -YQPLX
        =====
        UYUUQP
       -UGMYQL
        ======
         PFXRUY
        -PGYYUE
         ======
          UYFRGJ
         -UGMYQL
          ======
           PXQJX

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