CF1840A.Cipher Shifer

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.

存在一个字符串 $a$（你并不知道它），该字符串由小写拉丁字母组成，并按照以下规则被加密为字符串 $s$：

• 在字符串 $a$ 的每个字符之后，添加任意（可能为零）个与该字符不同的小写拉丁字母；
• 在每次这样的添加之后，再将我们刚刚补充的那个原始字符重新添加一次。

你将获得字符串 $s$，需要输出原始字符串 $a$。换言之，你需要对字符串 $s$ 进行解密。

注意：任何按此方式加密的字符串均可被唯一地解密。

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 $a$.

输入的第一行包含一个整数 $t$（$1 \le t \le 1000$）—— 测试用例的数量。

随后是各测试用例的描述。

每个测试用例的第一行包含一个整数 $n$（$2 \le n \le 100$）—— 加密消息的长度。

每个测试用例的第二行包含一个长度为 $n$ 的字符串 $s$ —— 该加密消息由某个字符串 $a$ 得到。

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

对于每个测试用例，在单独一行输出解密后的消息 $a$。

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.

在第一条加密消息中，字母 $a$ 被加密为 $aba$，字母 $c$ 被加密为 $cabac$。

在第二条加密消息中，仅有一个字母 $q$ 被加密为 $qzxcq$。

在第三条加密消息中，每个字母均未添加任何字符。