2-d parity codes       
----------------

Parity-based codes are used in many applications, including network 
communication. Unilike 1-d parity, 2-d parity can detect 2 errors and
correct 1 error. In this problem, you are required to implement and 
2-d parity-based error detector and corrector.

A 2-d parity encoding takes n n-bit strings (written in a 2-d form -- see 
the sample input)and adds a parity bit to each row and each column.

Input 
-----

Input consists of multiple cases. Each case starts with a line containing 
a positive integer n (n < 500) that indicates the number of bits used in the
2-d parity encoding scheme. This is followed by n+1 lines, each containing
n+1 bits separated by single spaces. These signify the data as well as the 
parity bits. The input data will have no more than 2 bit errors. For simplicity
you may assume that the parity bits contain no errors. You program will 
detect and, if possible, correct the error(s).

Input is terminated by a line containing two zeroes. This line should not be 
processed.

Output 
------

For each line of input produce one line of output containing one of the 
following responses: 

(1) No Bit errors
(2) Bit error at x,y 
(3) 2 errors detected but not corrected

For (2), the rows and columns are counted from 0 up and to the right and bottom
respectively.

Sample Input 
------------

4
1 1 1 1 0
0 0 0 0 0
1 1 1 1 0
0 0 0 0 0
0 0 0 0 0
5
1 1 1 1 1 1
0 0 0 0 0 1
1 1 1 1 1 1
0 0 0 0 0 0
1 1 1 1 1 1
1 1 0 1 1 0
0

Output for Sample Input
-----------------------

No Bit errors
Bit error at 1,2