complicated mask_attack or brute force?

[martintooth]

I am trying to figure out the appropriate mask for a 12 digit numeric password where one of the 12 digits is randomly assigned an upper case letter character instead of a number.

Example 12345A678901    or 401B23456598

The letter can appear anywhere in the password and there is only ever one letter

I feel like there has got to be a way to use a mask or an approach that requires less possible combinations than a straight brute force attack. Where I am lost is setting it up so that only one digit is ever treated as a letter character.

Any help would be greatly appreciated.

Thanks,