There are so many people that the tickets are all sold out !
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user
Luckily we got the last two .
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assistant
Look , Danny . The Four Great Inventions !
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user
Gunpowder , compass , the paper making , and the printing .
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assistant
I really admire those who made such great inventions !
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user
May , I don't see why they are great . They are just simple things .
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assistant
They look simple today . But they were milestones in their times .
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user
Milestones ? May , you must be kidding .
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assistant
Just think Bill Gates , those inventions are as important as the windows system .
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user
Well , I suppose the ancient inventors made a lot of money out of them .
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assistant
No , quite the contrary .
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user
Why ? Didn't you say that they were milestones ?
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assistant
Yes , but they went to the public without any patent protection .
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user
Well , their inventors were not as clever as Bill Gates .
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assistant