????????
      +---------
FFYPF | XUEUXEUJ
       -XYUMX
        =====
         XFPLE
        -RXRNR
         =====
          ERYPU
         -UJEQU
          =====
           RPULJ
          -RXRNR
           =====
           ?????

base: 13
letters: EFJLMNPQRTUXY
difficulty: medium
missing: T