回复：Problem 4

来源: HavingFun2 于 2009-08-18 12:32:56 [] [旧帖] [给我悄悄话] 阅读数 : (63 bytes)
回答: IMO 2009 由 康MM 于 2009-07-24 03:51:50

Ha, I just prove that there are two possible answers: 30 and 45

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