????????
      +---------
YUGLL | LEEHEGMU
       -YUGLL
        =====
        YHNXJG
       - MNUUJ
        ======
         YHJMJM
        - MNUUJ
         ======
           RUMRU
          -RJJXX
           =====
           ?????

base: 12
letters: EFGHJLMNRUXY
missing: F
difficulty: easy