?????????
      +----------
6E31B | 0692B50B9
       -57498
        =====
         0D075
        -57498
         =====
         662680
        -6A5E47
         ======
          6CE67B
         -694DD5
          ======
            4E8E9
           -02962
            =====
            ?????

base: 15
letters: 0123456789ABCDE
difficulty: medium