????????
      +---------
48B23 | 366B67D8
       -48B23
        =====
        BB1547
       -D70912
        ======
         B216AD
        -D70912
         ======
          287858
         -282288
          ======
          ??????

base: 14
letters: 0123456789ABCD
difficulty: medium
missing: C