2CE7
      +---------
87457 | 57812445
       -87457
        =====
        4D7084
       -638D0A
        ======
         4302A4
        -412C1D
         ======
          C79645
         -C610E7
          ======
           CC051

base: 15
letters: 0123456789ABCDE
difficulty: hard
missing: B