????????
      +---------
C6664 | 0675196C
       -C6664
        =====
         A2029
        -C6664
         =====
         9977A6
        -95000E
         ======
          BD376C
         -B7FFF2
          ======
          ??????

base: 16
letters: 0123456789ABCDEF
difficulty: hard
missing: 8