CF177A1.Good Matrix Elements

普及/提高-

通过率:0%

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题目描述

The Smart Beaver from ABBYY got hooked on square matrices. Now he is busy studying an n×nn×n size matrix, where nn 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 5×55×5 matrix. The good elements are marked with green. Help the Smart Beaver count the sum of good elements of the given matrix.

输入格式

The first line of input data contains a single odd integer nn . Each of the next nn lines contains nn integers aija_{ij} (0<=aij<=100)(0<=a_{ij}<=100) separated by single spaces — the elements of the given matrix.

The input limitations for getting 30 points are:

  • 1<=n<=51<=n<=5

The input limitations for getting 100 points are:

  • 1<=n<=1011<=n<=101

输出格式

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

输入输出样例

  • 输入#1

    3
    1 2 3
    4 5 6
    7 8 9
    

    输出#1

    45
    
  • 输入#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#2

    17
    

说明/提示

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

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