The letter H.
or
The barman says "Sorry we don't serve food in here"
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proving once and for all that you can't have your kayak and heat it.
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Because he never pays his debts.
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50. One to screw in the light bulb and the remaining 49 to guard him .
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1,000,001: One to change the bulb and 1,000,000 to rebuild civilization to the point where they need light bulbs again.
or