7C3A
      +---------
88323 | B2558A17
       -7B636
        =====
        88602A
       -896027
        ======
         899971
        - C01CA
         ======
           2ABA7
          -A0542
           =====
            6654

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