????????
      +---------
ED614 | 3CEA85D1
       -ED614
        =====
        FCCF35
       -F3A24F
        ======
         5BCE4D
        -289D10
         ======
          24E6C1
         -4C1C21
          ======
          ??????

base: 16
letters: 0123456789ABCDEF
difficulty: hard
missing: 7