21B2
      +---------
2BAC4 | A2C21802
       -2BAC4
        =====
         57688
        -49890
         =====
          534A0
         -5875C
          =====
           2B4B2
          -2BAC4
           =====
             1A4

base: 13
letters: 0123456789ABC
difficulty: medium