Cause: I returned to my roommate at noon and asked him to download a Baidu Library document that could only be downloaded with a download coupon, so I searched the Internet for a long time and directly connected Baidu Library to analyze it -- no result, there was something about freezing point library on the Internet, which I had downloaded before. The principle was to download it in txt format, which was totally useless. Baidu found several times that this site could be downloaded, but it required a fee, Then began a wave of solutions.
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