????????
      +---------
53AA3 | 032AC269
       -53AA3
        =====
         97992
        -49267
         =====
         5C7C96
        -5C09BD
         ======
           63099
          -8D446
           =====
           ?????

base: 14
letters: 0123456789ABCD
difficulty: hard
missing: 1