This will get you started. If you want more help, you'll need to put more effort into your question:
declare or otherwise obtain list of files
declare scalar for max (a, b) equal to undef
for every file{
open the file
for reach line{
split the line into scalars (current a, current b)
if current a > max a then set max b = current b
}
close the file
}
you now have b from the maximum seen value of a
Update:I'm not sure what the post has to do with hashes or hash files (I'm not even sure what is meant by a hash file), so my response didn't address that.