????????
      +---------
TYMXF | HTFPTHJH
       -TYMXF
        =====
        UJYRLH
       -UNRNQJ
        ======
         TUUGMJ
        -XWLQWT
         ======
          TUULNH
         -XWLQWT
          ======
          ??????

base: 15
letters: FGHJLMNPQRTUWXY
difficulty: hard