[1610] Glamor Sequence
- 时间限制: 1000 ms 内存限制: 65535 K
- 问题描述
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you have a sequence +1, +2, +3, ... +m, -(m + 1), -(m + 2), ..., -(2m), (2m + 1), (2m + 2), ..., (3m), .....
and you need calculator sum of the first n items.
- 输入
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For each test case, there is a line contains two integers n and m, (1 <= m <= n <= 1000000000).
- 输出
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For each test case, print sum of the first n items.
- 样例输入
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8 2 10 3
- 样例输出
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-8 5
- 提示
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For the first sample, the sequence is 1, 2, -3, -4, 5, 6, -7, -8, so the answer is -8. For the second sample, the sequence is 1, 2, 3, -4, -5, -6, 7, 8, 9, -10, so the answer is 5.
- 来源
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本站或者转载
- 操作
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