One. You don't believe me do you? I've got photos! See that big blob? Well, just squint your eyes a bit. . . .
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Three:
One to write the light bulb removal program,
one to write the light bulb insertion program, and
one to act as a light bulb administrator to make sure nobody else tries to change the light bulb at the same time.
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Only two, but the hard part is getting them into the light bulb.
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