Description: Description
Dr lee cuts a string S into N pieces,s[1],…,s[N].
Now, Dr lee gives you these N sub-strings: s[1],…s[N]. There might be several possibilities that the string S could be. For example, if Dr. lee gives you three sub-strings {“a”,“ab”,”ac”}, the string S could be “aabac”,”aacab”,”abaac”,…
Your task is to output the lexicographically smallest S.
Input
The first line of the input is a positive integer T. T is the number of the test cases followed.
The first line of each test case is a positive integer N (1 <=N<= 8 ) which represents the number of sub-strings. After that, N lines followed. The i-th line is the i-th sub-string s[i]. Assume that the length of each sub-string is positive and less than 100.
Output
The output of each test is the lexicographically smallest S. No redundant spaces are needed.
Sample Input
1
3
a
ab
ac
Sample Output
aabac
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test.cpp
要求说明.doc
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