Chess board (3) P19991

Consider a square chess board with $n$ rows and $n$ columns, where every square contains between 0 and 9 coins. Write a program such that, given a chess board, computes the total number of coins on its two diagonals.

Input

Input begins with the size $n$ of the board. Follow $n$ lines, each one with $n$ characters between ‘0’ and ‘9’.

Output

Print the total number of coins on the two diagonals of the board.