问题 A: Image Scaling

You are given a $n\times m$ matrix consisting of $\tt{.}$ and $\tt{x}$. All $\tt{x}$s form a submatrix and you want to extract it and scale down as much as possible while keeping integer side length and unchanged aspect ratio. Output the final matrix. It's guaranteed that there's at least one $\tt{x}$ in the matrix.

The first line contains two integers $n,m$. The following $n$ lines each contain a string of length $m$ consisting of $\tt{.}$ and $\tt{x}$.

A matrix consisting of $\tt{x}$.

$1\le n,m\le500$