A14637 | Strange LCS

You are given $n$ strings $s_1, s_2, \ldots, s_n$ , each consisting of lowercase and uppercase English letters. In addition, it's guaranteed that each character occurs in each string at most twice. Find the longest common subsequence of these strings.

A string $t$ is a subsequence of a string $s$ if $t$ can be obtained from $s$ by deletion of several (possibly, zero or all) symbols.

Each test consists of multiple test cases. The first line contains a single integer $t$ ( $1 \leq t \leq 5$ ) — the number of test cases. Description of the test cases follows.

The first line of each test case contains a single integer $n$ ( $2 \leq n \leq 10$ ) — the number of strings.

Each of the next $n$ lines contains the corresponding string $s_i$ . Each $s_i$ is non-empty, consists only of uppercase and lowercase English letters, and no character appears more than twice in each string.

For each test case print the answer in two lines:

In the first line print the length of the longest common subsequence.

In the second line print the longest common subsequence. If there are multiple such subsequences, print any of them.