Given a array of N strings, find the longest common prefix among all strings present in the array.
The first line of the input contains an integer T which denotes the number of test cases to follow. Each test case contains an integer N. Next line has space separated N strings.
Print the longest common prefix as a string in the given array. If no such prefix exists print "-1"(without quotes).
1 <= T <= 103
1 <= N <= 103
1 <= |S| <= 103
geeksforgeeks geeks geek geezer
apple ape april
Testcase 1: Longest common prefix in all the given string is gee.