CF177A2.Good Matrix Elements

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.

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:

• $1<=n<=101$

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

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