????????
      +---------
0611A | 27C33792
       -0611A
        =====
        0198C7
       -070293
        ======
         A76709
        -AAC221
         ======
          AA4802
         - 23BB7
          ======
          ??????

base: 13
letters: 0123456789ABC
difficulty: medium
missing: 5