CF1508A.Binary Literature

A bitstring is a string that contains only the characters 0 and 1.

Koyomi Kanou is working hard towards her dream of becoming a writer. To practice, she decided to participate in the Binary Novel Writing Contest. The writing prompt for the contest consists of three bitstrings of length $2n$. A valid novel for the contest is a bitstring of length at most $3n$ that contains at least two of the three given strings as subsequences.

Koyomi has just received the three prompt strings from the contest organizers. Help her write a valid novel for the contest.

A string $a$ is a subsequence of a string $b$ if $a$ can be obtained from $b$ by deletion of several (possibly, zero) characters.

位字符串（bitstring）是指仅由字符 0 和 1 组成的字符串。

小野美咲（Koyomi Kanou）正为实现自己成为作家的梦想而刻苦努力。为了练习，她决定参加“二进制小说写作大赛”。本次比赛的写作提示由三个长度均为 $2n$ 的位字符串组成。比赛中一个合法的小说，是指一个长度至多为 $3n$ 的位字符串，且该字符串至少以其中两个给定字符串作为子序列。

美咲刚刚从比赛主办方那里收到了这三个提示字符串。请帮她写出一篇符合要求的小说。

字符串 $a$ 是字符串 $b$ 的子序列，当且仅当 $a$ 可通过从 $b$ 中删除若干（可能为零个）字符而得到。

The first line contains a single integer $t$ ($1 \le t \le 10^4$) — the number of test cases.

The first line of each test case contains a single integer $n$ ($1 \le n \le 10^5$).

Each of the following three lines contains a bitstring of length $2n$. It is guaranteed that these three strings are pairwise distinct.

It is guaranteed that the sum of $n$ across all test cases does not exceed $10^5$.

第一行包含一个整数 $t$（$1 \le t \le 10^4$）—— 表示测试用例的数量。

每个测试用例的第一行包含一个整数 $n$（$1 \le n \le 10^5$）。

接下来的三行，每行包含一个长度为 $2n$ 的二进制字符串。保证这三个字符串两两不同。

保证所有测试用例的 $n$ 值之和不超过 $10^5$。

For each test case, print a single line containing a bitstring of length at most $3n$ that has at least two of the given bitstrings as subsequences.

It can be proven that under the constraints of the problem, such a bitstring always exists.

If there are multiple possible answers, you may output any of them.

对于每个测试用例，输出一行长度至多为 $3n$ 的比特串，该比特串至少以所给定的两个比特串作为子序列。

在本题的约束条件下，可以证明这样的比特串一定存在。

如果存在多个可能的答案，你可以输出其中任意一个。

In the first test case, the bitstrings 00 and 01 are subsequences of the output string: 010 and 010. Note that 11 is not a subsequence of the output string, but this is not required.

In the second test case all three input strings are subsequences of the output string: 011001010, 011001010 and 011001010.

在第一个测试用例中，位字符串 00 和 01 均为输出字符串 010 的子序列。注意，11 并不是输出字符串的子序列，但题目并不要求这一点。

在第二个测试用例中，全部三个输入字符串均为输出字符串 011001010 的子序列：011001010、011001010 和 011001010。