Slime

题意翻译

### 题目大意: 有$n$只史莱姆qwq,每只史莱姆有一个分数,每次一只史莱姆可以吞掉左边的或者右边的史莱姆(要是有的话),然后ta的分数会减去被吞的史莱姆的分数,问最后剩下的史莱姆分数最大为多少 ### 输入格式: 第一行一个整数$n$ 第二行$n$个整数,表示史莱姆的分数 ### 输出格式: 一个整数,即最大分数

题目描述

There are $ n $ slimes in a row. Each slime has an integer value (possibly negative or zero) associated with it. Any slime can eat its adjacent slime (the closest slime to its left or to its right, assuming that this slime exists). When a slime with a value $ x $ eats a slime with a value $ y $ , the eaten slime disappears, and the value of the remaining slime changes to $ x - y $ . The slimes will eat each other until there is only one slime left. Find the maximum possible value of the last slime.

输入输出格式

输入格式


The first line of the input contains an integer $ n $ ( $ 1 \le n \le 500\,000 $ ) denoting the number of slimes. The next line contains $ n $ integers $ a_i $ ( $ -10^9 \le a_i \le 10^9 $ ), where $ a_i $ is the value of $ i $ -th slime.

输出格式


Print an only integer — the maximum possible value of the last slime.

输入输出样例

输入样例 #1

4
2 1 2 1

输出样例 #1

4

输入样例 #2

5
0 -1 -1 -1 -1

输出样例 #2

4

说明

In the first example, a possible way of getting the last slime with value $ 4 $ is: - Second slime eats the third slime, the row now contains slimes $ 2, -1, 1 $ - Second slime eats the third slime, the row now contains slimes $ 2, -2 $ - First slime eats the second slime, the row now contains $ 4 $ In the second example, the first slime can keep eating slimes to its right to end up with a value of $ 4 $ .