????????
      +---------
0A7FF | 2FEF32CB
       -AD9FC
        =====
        7E9FF2
       -7469F4
        ======
          8BFFC
         -61EF5
          =====
          7BD10B
         -7B7EFA
          ======
          ??????

base: 16
letters: 0123456789ABCDEF
difficulty: hard
attributes: nested indirection