Cipher Shifer

对一个字符串 $a$ 进行加密后得到一个新字符串 $s$。 加密规则如下： - 在字符串 $a$ 的每个字符之后，添加任意(可能为零)数量的小写字母，与字符本身不同。 - 在每次这样的添加之后，我们将被补充的字符添加在已添加的字符后。 给出已加密字符串 $s$，求出加密之前的字符串。

There is a string $ a $ (unknown to you), consisting of lowercase Latin letters, encrypted according to the following rule into string $ s $ : - after each character of string $ a $ , an arbitrary (possibly zero) number of any lowercase Latin letters, different from the character itself, is added; - after each such addition, the character that we supplemented is added. You are given string $ s $ , and you need to output the initial string $ a $ . In other words, you need to decrypt string $ s $ . Note that each string encrypted in this way is decrypted uniquely.

The first line of the input contains a single integer $ t $ ( $ 1 \le t \le 1000 $ ) — the number of test cases. The descriptions of the test cases follow. The first line of each test case contains a single integer $ n $ ( $ 2 \le n \le 100 $ ) — the length of the encrypted message. The second line of each test case contains a string $ s $ of length $ n $ — the encrypted message obtained from some string $ a $ .

For each test case, output the decrypted message $ a $ on a separate line.

3
8
abacabac
5
qzxcq
20
ccooddeeffoorrcceess

ac
q
codeforces

In the first encrypted message, the letter $ a $ is encrypted as $ aba $ , and the letter $ c $ is encrypted as $ cabac $ . In the second encrypted message, only one letter $ q $ is encrypted as $ qzxcq $ . In the third encrypted message, zero characters are added to each letter.