????????
      +---------
57B74 | 9C2B5C45
       -A656C
        =====
        3CBB1C
       -3C6261
        ======
          4A394
         -57B74
          =====
          134065
         -1C4979
          ======
          ??????

base: 13
letters: 0123456789ABC
difficulty: intermediate
missing: 8