Background

Tom likes playing game ¡®Lian lian Kan¡¯; a very popular little games now. He plays the game well and usually can solve the puzzle quickly. But one day, he amazedly found that there weren¡¯t two same blocks can be connected (I never encounter that case) when the game started just a while, so he felt very angry.
He wanted to know whether the case was caused by the computer that had given the wrong initial blocks layout or his inattention. So he heads for you the genius program team to help him judge whether it was or not computer¡¯s fault.

Problem

Given an initial game layout of N*N blocks, which contains N*N/2 different pairs of icons (We use strings standing for icons). If two same icons are both on the border of the remaining icons (One icon on the border means among its four nearby positions up, down, left and right, at least one position isn¡¯t occupied by any remaining icons.) and can be connected by a curve only made up of several horizontal or vertical segments, the two can be removed. We assume that the outside of the border is empty (So the icons on the border can be connected each other at the beginning). If there are more than one pair can be removed at the same time, we remove the pair with the least lexical order string. The problem is whether all the pairs can be removed completely?

Input

The first line of the input contains an integer T (0<T<10), the number of the test cases, followed by T input blocks. Every block begins with an even integer N (0<N<50), and there are N strings separated by space (String only contain lowercase and length of string is less than 30) in the following N lines. The N*N strings indicates the initial game layout.

Output

For each test case, if all the pairs can be removed completely, output the strings one per line as the sequence they removed. Otherwise, just output a sentence ¡°Computer's fault¡±. Every output block is followed by a blank line.

Sample Input

1
2
at cs
cs at

Sample Output

at
cs

Hint

The icon ¡°at¡± and the icon ¡°cs¡± can be removed, but according to the problem, we should remove the icon ¡°at¡±, then the icon ¡°cs¡±.

From: WHUCPC'2005