????????
      +---------
XNMMH | QYQWLURW
       -XNMMH
        =====
        LYFMFU
       - MNWPN
        ======
         GJTWRR
        -GGNHUU
         ======
          XLRLLW
         -XTNTJL
          ======
          ??????

base: 15
letters: FGHJLMNPQRTUWXY
difficulty: medium