My best mate is a fan of his work. I like it too, but I have a problem in that since a particularly ... finger lickin' good scene in Consider Phlebas, my squick factor precludes me from reading any more of his work. Without any details, that particular scene pressed a particular dark, furry, oily and squirming button in my psyche, and I cannot get rid of the image in my mind, even years later.

*shudder*

Still, I heartily concur, on behalf of my friends, and myself before that button was squished. It is very sad news.

You've been given a list of words to study and memorize. Being a diligent student of language and the arts, you've decided to not study them at all and instead make up pointless games based on them. One game you've come up with is to see how you can concatenate the words to generate the lexicographically lowest possible string.

Input
As input for playing this game you will receive a text file containing an integer N, the number of word sets you need to play your game against. This will be followed by N word sets, each starting with an integer M, the number of words in the set, followed by M words. All tokens in the input will be separated by some whitespace and, aside from N and M, will consist entirely of lowercase letters.

Output
Your submission should contain the lexicographically shortest strings for each corresponding word set, one per line and in order.

Constraints
1 = N = 100
1 = M = 9
1 = all word lengths = 10

Example Input
5
6 facebook hacker cup for studious students
5 k duz q rc lvraw
5 mybea zdr yubx xe dyroiy
5 jibw ji jp bw jibw
5 uiuy hopji li j dcyi

Example Output
cupfacebookfor hackerstudentsstudious
duzklvrawqrc
dyroiymy beaxeyubxzdr
bwjibwjibwjijp
dcyihopjijliuiuy

(Please remove spaces from example outputs. slashdot filters ftl)