????????
      +---------
PRTXR | APFRRXMR
       -MFNRA
        =====
         NTHXX
        -PRTXR
         =====
         PTTRNM
        -PXMFRN
         ======
          PRHTXR
         -PATFMP
          ======
          ??????

base: 9
letters: AFHMNPRTX
difficulty: easy