0927
      +---------
86169 | 1AA63693
       -96551
        =====
        A91AA6
       -A6570A
        ======
         857359
        -800BA6
         ======
          A08083
         -A83B17
          ======
            0765

base: 12
letters: 0123456789AB
difficulty: challenging
missing: 4