Good Matrix Elements

题意翻译

对于一个n*n的矩阵，求出处于矩阵对角线，中间行和中间列的所有元素之和(保证n是个奇数)

题目描述

The Smart Beaver from ABBYY got hooked on square matrices. Now he is busy studying an $ n×n $ size matrix, where $ n $ is odd. The Smart Beaver considers the following matrix elements good: - Elements of the main diagonal. - Elements of the secondary diagonal. - Elements of the "middle" row — the row which has exactly  rows above it and the same number of rows below it. - Elements of the "middle" column — the column that has exactly  columns to the left of it and the same number of columns to the right of it.  The figure shows a $ 5×5 $ matrix. The good elements are marked with green. Help the Smart Beaver count the sum of good elements of the given matrix.

输入输出格式

输入格式

The first line of input data contains a single odd integer $ n $ . Each of the next $ n $ lines contains $ n $ integers $ a_{ij} $ $ (0<=a_{ij}<=100) $ separated by single spaces — the elements of the given matrix. The input limitations for getting 30 points are: - $ 1<=n<=5 $ The input limitations for getting 100 points are: - $ 1<=n<=101 $

输出格式

Print a single integer — the sum of good matrix elements.

输入输出样例

输入样例 #1

3
1 2 3
4 5 6
7 8 9

输出样例 #1

45

输入样例 #2

5
1 1 1 1 1
1 1 1 1 1
1 1 1 1 1
1 1 1 1 1
1 1 1 1 1

输出样例 #2

17

说明

In the first sample all matrix elements will be good. Good elements in the second sample are shown on the figure.