JLGL
      +---------
FRWTF | PRRTQNRL
       -FRWTF
        =====
        HLMRJN
       -HGQGJG
        ======
         HJFRTR
        -TYFHMY
         ======
          HLGMHL
         -HGQGJG
          ======
           HHNTH

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