Given an input stream of N characters consisting only of lower case alphabets. The task is to find the first non repeating character, each time a character is inserted to the stream. If no non repeating element is found print -1.
The first line of input contains an integer T denoting the no of test cases. Then T test cases follow. Each test case contains an integer N denoting the size of the stream. Then in the next line are x characters which are inserted to the stream.
For each test case in a new line print the first non repeating elements separated by spaces present in the stream at every instinct when a character is added to the stream, if no such element is present print -1.
1 <= T <= 200
1 <= N <= 500
a a b c
a a c
a -1 b b
a -1 c
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