????????
      +---------
UNUJN | QYTULYUY
       -PWMMW
        =====
        TYUFNY
       -THNTPL
        ======
         TJLQQU
        -TMLJLU
         ======
          TWWLHY
         -TMLJLU
          ======
          ??????

base: 13
letters: FHJLMNPQRTUWY
difficulty: medium
missing: R