Trả lời: VNOI Marathon 2009 - Q&A 11 năm, 6 tháng trước
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I think, "số tự nhiên" must be translated to "natural numbers", or non-negative integers. If not, contestant can think about integer in general, and it includes negative ones.
Trả lời: VNOI Marathon 2009 - Q&A 11 năm, 6 tháng trước
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Thanks for your suggestion, but we apologize since we want to put them in the OI section of VN SPOJ. We already put these questions in the partial problem set of SPOJ.
We hope SPOJ will include the scoring of the partial problem set into its ranking system soon.