????????
      +---------
TMFWF | LPTPPQHH
       -TMFWF
        =====
        PMPXUQ
       -MFQPRM
        ======
         RLQPPH
        -RPLWYH
         ======
          WQXHJH
         -UFHFJL
          ======
          ??????

base: 13
letters: FHJLMPQRTUWXY
difficulty: medium