Maximal square

Input

First line contains two integers $n$ and $m$ ($1$ ≤ $n$, $m$ ≤ $1500$). Each of the next $n$ lines contains $m$ digits $0$ and $1$ space separated.

Output

Print one integer – the size of maximal square that contains on its sides ones only. If there are no such squares, print $0$.

Examples