Iahub got bored, so he invented a game to be played on paper.
He writes n integers a1,?a2,?...,?an. Each of those integers can be either 0 or 1. He's allowed to do exactly one move: he chooses two indices i and j (1?≤?i?≤?j?≤?n) and flips all values ak for which their positions are in range [i,?j] (that is i?≤?k?≤?j). Flip the value of xmeans to apply operation x?=?1 - x.
The goal of the game is that after exactly one move to obtain the maximum number of ones. Write a program to solve the little game of Iahub.
The first line of the input contains an integer n (1?≤?n?≤?100). In the second line of the input there are n integers: a1,?a2,?...,?an. It is guaranteed that each of those n values is either 0 or 1.
Print an integer ― the maximal number of 1s that can be obtained after exactly one move.
In the first case, flip the segment from 2 to 5 (i?=?2,?j?=?5). That flip changes the sequence, it becomes: [1 1 1 0 1]. So, it contains four ones. There is no way to make the whole sequence equal to [1 1 1 1 1].
In the second case, flipping only the second and the third element (i?=?2,?j?=?3) will turn all numbers into 1.
解题思路：题意是讲有1个0,1序列，现允许你对任意1个子序列取反，问操作后得到的序列，最多能有多少个1。
数据不大，直接暴力。直接两层循环枚举取反序列的出发点和终点，统计每种情况下1的个数，保存1个最大值便可。
AC代码：