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Feel Good Description Bill is developing a new mathematical theory for human emotions. His recent investigations are dedicated to studying how good or 阅读全文
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C. Mail Stamps One day Bob got a letter in an envelope. Bob knows that when Berland's post officers send a letter directly from city «A» to city «B», 阅读全文
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2751: [HAOI2012]容易题(easy) Description 为了使得大家高兴，小Q特意出个自认为的简单题（easy）来满足大家，这道简单题是描述如下：有一个数列A已知对于所有的A[i]都是1~n的自然数，并且知道对于一些A[i]不能取哪些值，我们定义一个数列的积为该数列所有元素的乘积 阅读全文