????????
      +---------
D91B2 | 4C556C41
       -D91B2
        =====
        DC4C2C
       -DB1D67
        ======
         D98A94
        -DC1A70
         ======
          D03DC1
         -DB1D67
          ======
          ??????

base: 14
letters: 0123456789ABCD
difficulty: medium