F1E1
      +---------
65EF6 | C6715B80
       -65EF6
        =====
        574F3B
       -FE360E
        ======
         4D7178
        -3E3BAC
         ======
          FEED90
         -FE360E
          ======
            BA6A

base: 16
letters: 0123456789ABCDEF
difficulty: medium
missing: 2