?????????
      +----------
D8737 | D9B60B210
       -D8737
        =====
         9C29B2
        -9982C2
         ======
          60C781
         -5C8C6A
          ======
           5A30C0
          -538A2D
           ======
           ??????

base: 14
letters: 0123456789ABCD
missing: 4
difficulty: hard
hints: 4 << 0, 5 << D