The doors of 4 lockers in a school gym were worn out and have been replaced. The craftsman purchased the new metal digits required for the re-numbering of the doors. The numbering is consecutive. The store charges each digit "n" with n dollars (that is, digit "1" costs 1 dollar, while digit "0" is free). The craftsman paid 12 dollars for the numbering of the 4 doors. What were the numbers of the lockers?