[error] DEADLOCK/NODUP: no remaining values
        ????????
      +---------
A94C6 | DAB5B337
       -1C874
        =====
         D8573
        -1C874
         =====
         5530B3
        - 1C874
         ======
          40A4B7
         -B68DB1
          ======
          ??????

base: 14
letters: 0123456789ABCD
difficulty: medium
hints: 2 << 4, 6 << 9
missing: 2