???????
      +--------
WRNWW | FYTWFYF
       -WRNWW
        =====
        WUULWY
       -QYLLHQ
        ======
         JLYRNF
        -UYMMPG
         ======
         ??????

base: 15
letters: FGHJLMNPQRTUWXY
difficulty: medium
hints: H << P, F << G, X << M
missing: X