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Problem description Little Chris is bored during his physics lessons (too easy), so he has built a toy box to keep himself occupied. The box is specia 阅读全文
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Problem description Mad scientist Mike entertains himself by arranging rows of dominoes. He doesn't need dominoes, though: he uses rectangular magnets 阅读全文
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Problem description Vasya is very upset that many people on the Net mix uppercase and lowercase letters in one word. That's why he decided to invent a 阅读全文