640D
      +---------
87105 | 535F8883
       -582F9
        =====
         A9CA8
        -F1BB0
         =====
          7A928
         -424DC
          =====
           1C663
          -1EE1A
           =====
            C8B6

base: 16
letters: 0123456789ABCDEF
difficulty: hard