UFJ
      +--------
MMXLN | UXFMJRR
       -UWTUH
        =====
         RHJWR
        -FHMGW
         =====
         MGNWWR
        -MGTXWU
         ======
           URGY

base: 13
letters: FGHJLMNRTUWXY
difficulty: medium
missing: Y