Kelukin is a businessman. Every day, he travels around cities to do some business. On August 17th, in memory of a great man, citizens will read a book named "the Man Who Changed China". Of course, Kelukin wouldn't miss this chance to make money, but he doesn't have this book. So he has to choose two city to buy and sell.
As we know, the price of this book was different in each city. It is $a_i$ $yuan$ in $i$$t$ city. Kelukin will take taxi, whose price is $1$$yuan$ per km and this fare cannot be ignored.
There are $n-1$ roads connecting $n$ cities. Kelukin can choose any city to start his travel. He want to know the maximum money he can get.