????????
      +---------
CA1A6 | DD28BB67
       -76C63
        =====
        C33CAB
       -CBA792
        ======
         C2A666
        -C3558B
         ======
          C49AD7
         -CC4100
          ======
          ??????

base: 14
letters: 0123456789ABCD
difficulty: hard
hints: 0 << B