BAA3
      +---------
B08C1 | 14089301
       -B08C1
        =====
        B08673
       -BC4928
        ======
         B092B0
        -BC4928
         ======
          BC5681
         -B60310
          ======
           B7CC2

base: 13
letters: 0123456789ABC
difficulty: medium
missing: A