[[Category: Euler Circuit]]
A catenym is a pair of words separated by a period such that the last letter of the first word is the same as the first letter of the second. For example, the following are catenyms:
dog.gopher
gopher.rat
rat.tiger
aloha.aloha
arachnid.dog
A compound catenym is a sequence of three or more words separated by periods such that each adjacent pair of words forms a catenym. For example,
aloha.aloha.arachnid.dog.gopher.rat.tiger
Given a dictionary of lower case words, you are to find a compound catenym that contains each of the words exactly once.
The first line of standard input contains t (t<=100), the number of test cases. Each test case begins with 3 ≤ n ≤ 1000 - the number of words in the dictionary. n distinct dictionary words follow; each word is a string of between 1 and 20 lowercase letters on a line by itself.
For each test case, output a line giving the lexicographically least compound catenym that contains each dictionary word exactly once. Output '***' if there is no solution.