???????
      +--------
LGJWY | HPTMJHH
       -PHYHL
        =====
        YQHPFH
       -YQGHMF
        ======
          GQXPH
         -LGJWY
          =====
          ?????

base: 13
letters: EFGHJLMPQTWXY
difficulty: hard
missing: E