FHWG
      +---------
NNWTW | MTQQNGJF
       -FMUWU
        =====
        NNULTG
       -NPULTF
        ======
         NPPPFJ
        - HLJHG
         ======
           TGMGF
          -GLQRT
           =====
            UUQR

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