D7AF
      +---------
6BB47 | 94875B39
       -6BB47
        =====
        16E73B
       -1D7BFD
        ======
         1031E3
        -D224FA
         ======
          601389
         -1FF4EF
          ======
           693B7

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