????????
      +---------
QTTXR | TLPFLPYY
       -QTTXR
        =====
        FELXRP
       -FWRQFL
        ======
         FQLETY
        -FWRQFL
         ======
          PQYREY
         -PXQLPF
          ======
          ??????

base: 10
letters: EFLPQRTWXY
difficulty: hard