## Problem Description

In the big playground,there are many boys and girls,they just form a N*N square.
A so-called "BG Square" is a square in which all boys are separated by girls and vice versa,ignoring the people outside.
Now wzc is wondering what is the biggest size of "BG Square" that you can find in the playground.
## Input

There are multiple test cases.
For each case, the first line is a integers N (1<= N <= 1000),indicating there is a N*N square,
which is made of boys and girls in the playground.
Followed by N lines,each line contains N char of 'B' or 'G'.
'B' stands for boy,and 'G' for girl.
## Output

For each test case, output the biggest size of "BG Square" that you can find in the playground.

## Sample Input

1
B
2
BG
GB
4
BGBB
GBGB
BGBG
GBBG
5
BGBGB
GBGBG
BGBGB
GBGBG
BGBGB

## Sample Output

1
2
3
5

## Source

FZU 2009 Summer Training Qualification -- Hero Revival 2