Migrated from Lutece 1042 Ideal matrix

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Description

Dave has a big matrix with a lowercase in each cell. In this matrix, he find some small matrix very attractive, he call them ieadl matrix.

A matrix is a ieadl matrix when it matches following conditions.

1. For each row, nomatter you read it from right to left or from left to right, it would be same;
2. For each column, nomatter you read it from bottom to front or from front to bottom, it would be same;

example:

  a b a    a b b
  c c c    c c c        
  a b a    a b a

Frist one is a ideal matrix. And second is not,beacuse in first row, when you read it from left to right,it is abb ,and when you read it from right to left it is bba. now he want to konw biggest size ideal matrix he can find in this big matrix.

Input

Frist line has tow element $n$, indicate number of rows and number of column.

Following $n$ line, each have $n$ lowercase.

$1 \leq n \leq 200$

Output

One number, indecate the answer.

Samples

4
dbda
cfcb
dbdc
defg

9

3
abc
def
ghi

1

4
abcd
efgh
abcd
abcd

3

Resources

The 13th UESTC Programming Contest Preliminary