Description:
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 $${ \frac { n - 1 } { 2 } }$$ rows above it and the same number of rows below it.
- Elements of the "middle" column — the column that has exactly $${ \frac { n - 1 } { 2 } }$$ 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.
Input Format:
The first line of input data contains a single odd integer n. Each of the next n lines contains n integers aij (0 ≤ aij ≤ 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
Output Format:
Print a single integer — the sum of good matrix elements.
Note:
In the first sample all matrix elements will be good. Good elements in the second sample are shown on the figure.