????????
      +---------
WPEHW | WMQMMYFY
       -WPEHW
        =====
         QUULY
        -WPEHW
         =====
         PYPQWF
        -PLQEEW
         ======
          PEUYHY
         -PLQEEW
          ======
          ??????

base: 12
letters: EFHLMNPQUWXY
missing: X N
difficulty: challenging
hints: X << P, F, N