630A
      +---------
AACBA | 8314168C
       -AACBA
        =====
         7B656
        -9C0C9
         =====
         361008
        -32313B
         ======
          6A451C
         -6A0205
          ======
            0560

base: 13
letters: 0123456789ABC
difficulty: medium