Square

The table has $m$ rows and $n$ columns. It is made of identical small squares, and each square contains either 0 or 1. Consider a square whose sides are parallel to the rows and columns of the table and which is made of cells of the table. The side of the square must contain an odd number of cells, and both diagonals of the square must consist only of cells that contain 1. Write a program square that finds the maximum possible side length of such a square, measured in cells.

The first line contains the values of $n$ and $m$ separated by a space. The next $m$ lines each contain $n$ digits. Each digit is 0 or 1, and the digits in each line are written without separators. The table contains at least one 1.

A single integer, the maximum side length sought.

$2 < m < 3000$ $2 < n < 3000$