6038: Ciel and Flipboard
内存限制：256 MB
时间限制：2 S
题面：传统
评测方式：文本比较
上传者：
提交：1
通过：1
题目描述
D. Ciel and Flipboard
time limit per test
4 seconds
memory limit per test
256 megabytes
input
standard input
output
standard output
Fox Ciel has a board with n rows and n columns, there is one integer in each cell.
It's known that n is an odd number, so let's introduce
. Fox Ciel can do the following operation many times: she choose a sub-board with size x rows and x columns, then all numbers in it will be multiplied by -1.
Return the maximal sum of numbers in the board that she can get by these operations.
It's known that n is an odd number, so let's introduce
. Fox Ciel can do the following operation many times: she choose a sub-board with size x rows and x columns, then all numbers in it will be multiplied by -1. Return the maximal sum of numbers in the board that she can get by these operations.
Input
The first line contains an integer n, (1≤n≤33, and n is an odd integer) − the size of the board. Each of the next n lines contains n integers − the numbers in the board. Each number doesn't exceed 1000 by its absolute value.
Output
Output a single integer: the maximal sum of numbers in the board that can be accomplished.
Examples
Input
3 -1 -1 1 -1 1 -1 1 -1 -1
Output
9
Input
5 -2 0 0 0 -2 0 -2 0 -2 0 0 0 -2 0 0 0 -2 0 -2 0 -2 0 0 0 -2
Output
18
Note
In the first test, we can apply this operation twice: first on the top left 2×2 sub-board, then on the bottom right 2×2 sub-board. Then all numbers will become positive. 
输入样例 复制
输出样例 复制