????????
      +---------
BB732 | 7BAD1B26
       -472B3
        =====
         6D66B
        -BB732
         =====
         3A4C72
        -3CA70A
         ======
          356436
         -0898DD
          ======
          ??????

base: 14
letters: 0123456789ABCD
difficulty: medium