[error] DEADLOCK/NODUP: no remaining values
        ????????
      +---------
302A2 | 08093627
       -661B1
        =====
        7415B6
       -7674A6
        ======
         741392
        -7674A6
         ======
          745187
         -7674A6
          ======
          ??????

base: 12
letters: 0123456789AB
difficulty: medium