????????
      +---------
038D2 | 617A7999
       -038D2
        =====
        28C0C9
       -86B05C
        ======
         2B5969
        -86B05C
         ======
          B17C69
         -3C6B70
          ======
          ??????

base: 14
letters: 0123456789ABCD
difficulty: intermediate
missing: 4