题目网址: http://www.puzzleup.com/2016/ http://www.puzzleup.com/2016/puzzle/?17 答题时限: 11月17日７ＰＭ－比赛结束（约12月14日） 加分时限: 11月17日７ＰＭ－11月23日６：５９ＰＭ 答对可得基本分１００分。答案可上传５次，每改１次答案从基本分扣２０分。　 比赛期间内可随时上传答案，加分时限内答对第ｎ天加（６－ｎ）分　 　　 　　 另依题目的难易有额外加分（如有８０％的人这题答错，答对者加８０分）　　 ◆SEVEN There is a number with digits appearing at most twice and all the numbers formed by adjacent two digits are divisible by 7. What can be the maximum value for this number? Example:63563 is such a number (63, 35, 56 and 63 are divisible by 7) but it is not the maximum. 有此一数，其每个数字至多出现两次，且所有相邻两位数所形成的数皆可被 7 整除。 问此数最大为何？ 例: 63563 为符合条件的一数 (63、35、56、63 皆可被 7 整除)，但并非最大。 -- 'You've sort of made up for it tonight,' said Harry. 'Getting the sword. Finishing the Horcrux. Saving my life.' 'That makes me sound a lot cooler then I was,' Ron mumbled. 'Stuff like that always sounds cooler then it really was,' said Harry. 'I've been trying to tell you that for years.' -- Harry Potter and the Deathly Hollows, P.308 --

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