先输入计算次数，然后输入数组个数，最后输出的是排好序的最小数组-Descr iption



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