D550
      +---------
31BD2 | 11D776A5
       -31BD2
        =====
        8BE066
       -8C8043
        ======
         84B09A
        -8C8043
         ======
          6CBB85
         -68C573
          ======
           2021E

base: 16
letters: 0123456789ABCDEF
difficulty: hard
missing: F