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A wqb-number, or B-number for short, is a non-negative integer whose decimal form contains the sub- string "13" and can be divided by 13. For example, 阅读全文
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杭州人称那些傻乎乎粘嗒嗒的人为62（音：laoer）。杭州交通管理局经常会扩充一些的士车牌照，新近出来一个好消息，以后上牌照，不再含有不吉利的数字了，这样一来，就可以消除个别的士司机和乘客的心理障碍，更安全地服务大众。不吉利的数字为所有含有4或62的号码。例如：62315 73418 88914都属 阅读全文
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ZS the Coder has recently found an interesting concept called the Birthday Paradox. It states that given a random set of 23 people, there is around 50 阅读全文
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The citizens of a small village are tired of being the only inhabitants around without a connection to the Internet. After nominating the future netwo 阅读全文
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Jzzhu has picked n apples from his big apple tree. All the apples are numbered from 1 to n. Now he wants to sell them to an apple store. Jzzhu will pa 阅读全文
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As you know, Vova has recently become a new shaman in the city of Ultima Thule. So, he has received the shaman knowledge about the correct bracket seq 阅读全文
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Alice and Bonnie are sisters, but they don't like each other very much. So when some old family photos were found in the attic, they started to argue 阅读全文
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Vasya is studying in the last class of school and soon he will take exams. He decided to study polynomials. Polynomial is a function P(x) = a0 + a1x1 阅读全文
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Let's assume that v(n) is the largest prime number, that does not exceed n; u(n) is the smallest prime number strictly greater than n. Find . Let's as 阅读全文
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John Doe has found the beautiful permutation formula. Let's take permutation p = p1, p2, ..., pn. Let's define transformation f of this permutation: w 阅读全文