In the square table $n \cdot n$ find the sum of integers at the main and the secondary diagonals. \InputFile The first line contains the size $n~(1 \le n \le 500)$ of the matrix. The next lines describe a matrix $n \cdot n$. The elements of the matrix are not greater than $10^5$ by absolute value. \OutputFile Print the sum of the integers at the main and the secondary diagonals. \includegraphics{https://static.eolymp.com/content/p5/p5qcfc9kep5fb8jfqq9ac5ehqs.gif}