摘要：
Problem description An elephant decided to visit his friend. It turned out that the elephant's house is located at point 0 and his friend's house is l 阅读全文
摘要：
Problem description For a positive integer n let's define a function f: f(n) = - 1 + 2 - 3 + .. + ( - 1)nn Your task is to calculate f(n) for a given 阅读全文
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Problem description Little Petya very much likes gifts. Recently he has received a new laptop as a New Year gift from his mother. He immediately decid 阅读全文