Description: A subsequence is a sequence that can be obtained from another sequence by removing some elements without changing the order of the remaining elements. A palindromic sequence is a sequence that is equal to the reverse of itself. You are given a sequence of $$$n$$$ integers $$$a_1, a_2, \dots, a_n$$$. Any integer value appears in $$$a$$$ no more than twice. What is the length of the longest palindromic subsequence of sequence $$$a$$$? Input Format: The first line contains a single integer $$$t$$$ ($$$1 \le t \le 1000$$$) — the number of testcases. Then the descriptions of $$$t$$$ testcases follow. The first line of each testcase contains a single integer $$$n$$$ ($$$1 \le n \le 250\,000$$$) — the number of elements in the sequence. The second line of each testcase contains $$$n$$$ integers $$$a_1, a_2, \dots, a_n$$$ ($$$1 \le a_i \le n$$$). Any integer value appears in $$$a$$$ no more than twice. The sum of $$$n$$$ over all testcases doesn't exceed $$$250\,000$$$. Output Format: For each testcase print a single integer — the length of the longest palindromic subsequence of sequence $$$a$$$. Note: Here are the longest palindromic subsequences for the example testcases: - 2 1 3 1 5 2 - 1 3 3 4 4 1 or 1 3 3 4 4 1 - 1 - 1 1 - 4 4 2 5 7 2 3 or 4 4 2 5 7 2 3