????????
      +---------
WWWXY | WRPPMLYM
       -WWWXY
        =====
         NHTPL
        -NNRHT
         =====
          NUWMY
         -NNRHT
          =====
           HTPUM
          -HHPLX
           =====
           ?????

base: 12
letters: HJLMNPRTUWXY
difficulty: medium
missing: J