"10" binary is 2.

>Sergey has a signature that contains the following text:
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>There are 10 types of people: Those who can read binary, and those who can't.
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>I always thought I understood the joke, but a colleague pointed out the real joke to me. Now I know that I'm one of those who can't. :)
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>Do you see the real joke?
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>(Sergey, you're not allowed to be the first to respond. :)