Puzzleup 2017 (3) Four Digits - 拼圖

題目網址: http://www.puzzleup.com/2017/
http://www.puzzleup.com/2017/puzzle/?3
答題時限: ８月24日７ＰＭ－比賽結束（約12月27日）
加分時限: ８月24日７ＰＭ－８月29日６：５９ＰＭ

答對可得基本分１００分。答案可上傳５次，每改１次答案從基本分扣２０分。　
比賽期間內可隨時上傳答案，加分時限內答對第ｎ天加（６－ｎ）分　 　　 　　
另依題目的難易有額外加分（如有８０％的人這題答錯，答對者加８０分）　　

◆FOUR DIGITS

A number has distinct digits and for its any four consecutive digits, the
multiplication of the two digits in the middle is greater than the sum of the
four digits.

What is the greatest such number?

一數的所有數位皆不同，
且對任意四個連續位數，中間兩位數的乘積皆大於四位數之和。

試問此數最大為多少？

--
'Oh, Harry, don't you see?' Hermione breathed. 'If she could have done
one thing to make absolutely sure that every single person in this school
will read your interview, it was banning it!'
---'Harry Potter and the order of the phoenix', P513

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