HMR
      +---------
QYPHF | HEUHEQLX
       - QYPHF
        ======
         UFXPPL
        -TXPXYY
         ======
          YYPURX
         -YWYQTQ
          ======
           FUFLP

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