Splitting work to pass through the integer overflow error

[drsnooker]

You could manually split the mask into multiple runs (if you have the hardware to complete the task before the heat death of the universe) by say fixing the first char of the mask.
a?a?a?a?a?a?a?a?a?a
b?a?a?a?a?a?a?a?a?a
c?a?a?a?a?a?a?a?a?a
d?a?a?a?a?a?a?a?a?a
...