CF327A.Flipping Game

Iahub got bored, so he invented a game to be played on paper.

He writes n integers _a_1, _a_2, ..., a__n. 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 a__k for which their positions are in range [i, j] (that is i ≤ k ≤ j). Flip the value of x means 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.

伊阿胡布感到无聊，于是发明了一个可以在纸上玩的游戏。

他写下 $n$ 个整数 $a_1,\,a_2,\,\dots,\,a_n$。其中每个整数只能是 $0$ 或 $1$。他恰好可以执行一次操作：选择两个下标 $i$ 和 $j$（满足 $1\,\le\,i\,\le\,j\,\le\,n$），并将所有位置在区间 $[i,\,j]$ 内的值 $a_k$（即满足 $i\,\le\,k\,\le\,j$ 的所有 $a_k$）进行翻转。对值 $x$ 进行翻转是指执行操作 $x\,=\,1\,-\,x$。

游戏的目标是：在恰好执行一次操作后，使得序列中 $1$ 的个数达到最大。请编写一个程序来解决伊阿胡布的这个小游戏。

The first line of the input contains an integer n (1 ≤ n ≤ 100). In the second line of the input there are n integers: _a_1, _a_2, ..., a__n. It is guaranteed that each of those n values is either 0 or 1.

输入的第一行包含一个整数 $n$（$1 \leq n \leq 100$）。输入的第二行包含 $n$ 个整数：$a_1,\,a_2,\,\ldots,\,a_n$。保证这 $n$ 个值中的每一个均为 $0$ 或 $1$。

Print an integer — the maximal number of 1s that can be obtained after exactly one move.

输出一个整数——恰好进行一次操作后所能得到的最多 1 的个数。

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.

在第一种情况下，翻转从第 2 位到第 5 位的区间（即 $i = 2,\, j = 5$）。该翻转操作改变序列，使其变为：

$$1\ 1\ 1\ 0\ 1$$

因此，序列中包含四个 1。无法通过任何操作使整个序列为 $$1\ 1\ 1\ 1\ 1$$。

在第二种情况下，仅翻转第二位和第三位元素（即 $i = 2,\, j = 3$）即可将所有数字变为 1。