9B91
      +---------
21073 | A45D2595
       -A1AB7
        =====
         8F705
        -94D11
         =====
          FE4B9
         -A1AB7
          =====
          2274D5
         -2C047D
          ======
            4C92

base: 16
letters: 0123456789ABCDEF
difficulty: hard
missing: 6