0095
      +---------
42749 | A883506A
       -42749
        =====
        089A10
       - 42749
        ======
         523B86
        -556237
         ======
          6BBA0A
         -7A4312
          ======
           C6879

base: 13
letters: 0123456789ABC
difficulty: medium
restrictions: no multiplication