AAQQZ

The 2015 International Olympiad in Informatics is held in Kazakhstan. The name "Kazakh" is sometimes spelled "QAZAQ" in the Latin alphabet, and QAZAQ is a palindrome. JOI learns this and starts to like palindromes, so he decides to build palindromes from strings he finds.

JOI finds a string of length N. Each character is assigned an integer from 1 to C, and the string written as integers is $S = (S_1, S_2, ..., S_N)$. The sequence $(S_i, S_{i+1}, ..., S_j)$ taken from the i-th to the j-th element ($1 ≤ i ≤ j ≤ N$) is called segment $(i, j)$. Segment $(i, j)$ is a palindrome when it equals its reversal, that is, when $(S_i, S_{i+1}, ..., S_j) = (S_j, S_{j-1}, ..., S_i)$ holds.

JOI builds a palindrome with the following operation.

1. First, choose one segment of S. Call the chosen segment T.
2. Let T' be T sorted in ascending order.
3. Replace segment T in sequence S with T'. Call the result S'. In other words, if JOI chooses segment $(i, j)$, sort $S_i, ..., S_j$ into $T'_i ≤ T'_{i+1} ≤ ... ≤ T'_j$, and set $S' = (S_1, ..., S_{i-1}, T'_i, ..., T'_j, S_{j+1}, ..., S_N)$.
4. Then, find a segment of S' that is a palindrome.

JOI wants to build the longest possible palindrome with this operation.

Given the sequence S that represents the string JOI found, find the maximum length of a palindrome JOI can build.

The first line contains two integers N and C, separated by a space. N is the length of the string JOI found, and C is the upper limit of the integers assigned to the characters.

The next N lines contain the sequence S. The i-th of these lines contains the integer $S_i$, the i-th element of S.

Print one integer on one line: the maximum length of a palindrome JOI can build.

• $1 ≤ N ≤ 3000$.
• $1 ≤ C ≤ 3000$.
• $1 ≤ S_i ≤ C$ ($1 ≤ i ≤ N$).