YXE
       +---------
RXNRHX | QNUECPUE
        -RXNRHX
         ======
         RUCHQXU
        -CQPNPEE
         =======
          RXXYXYE
         -RPUHCYR
          =======
           RQQHUQ

base: 10
letters: CEHNPQRUXY
difficulty: intermediate
restrictions: no multiplication