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

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

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

见题面 Input 部分

见题面 Output 部分

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