????????
      +---------
071D7 | 856D19A3
       -071D7
        =====
        0DC8A9
       -279D50
        ======
         03BB0A
        -279D50
         ======
          D722D3
         -D22A55
          ======
          ??????

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