问题 K: 8-bit Zoom

You are given a picture with size $n\times n$. You need to output the zoomed picture with the zooming rate $Z\%$ in 8-bit style, or determine the picture can not be zoomed. Here in 8-bit style, the size of the result picture is (nZ/100)×(nZ/100). A picture can not be zoomed in 8-bit style if and only if any of the following holds:

• nZ/100 is not an integer.
• In the zoomed picture, the color of some pixels can not be determined. Note that there aren't any interpolation algorithm applied in 8-bit style, so when at least two different colors are mapped into the same pixel in the resulting picture, the color of this pixel is undetermined.

The first line contains a single integer $T$ ($1\le T\le 10$), the number of test cases. For each test case:

The first line contains two integers $n$ and $Z$ ($1\le n\le 50$, $100\le Z\le 200$, $Z\mathrm{mod}25=0$), denoting the size of the original picture and the zooming rate.

Each of the following $n$ lines contains a string of length $n$, consisting of lowercase English letters. The $j$-th character in the $i$-th line denotes the color of the pixel located at $(i,j)$.

For each test case, if the picture can not be zoomed, print ''$\text{error}$'' in a line, otherwise print nZ/100 lines, each line contains a string of length nZ/100, denoting the resulting picture.