PRPR
       +-----------
QRPHUP | TNNQRWPTWP
        -TTRPHRP
         =======
          PUUQPHT
         -MRWPUHP
          =======
           TFUTFNW
          -TTRPHRP
           =======
            PTNFHRP
           -MRWPUHP
            =======
             QQTFRH

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