XRY
      +--------
YWXFX | RMFHEXR
       -YWXFX
        =====
         FGJLX
        -FXMER
         =====
          NHEER
         -NNRRY
          =====
           YFFX

base: 13
letters: EFGHJLMNQRWXY
difficulty: medium
missing: Q