????????
      +---------
GNFWJ | WGXWEJJG
       -EWHWF
        =====
        HGWRJJ
       -HFHGEY
        ======
         HEEYQJ
        -HMQNEM
         ======
          XWMFXG
         -XQPXQG
          ======
          ??????

base: 13
letters: EFGHJMNPQRWXY
difficulty: medium