C. Paint the Middletime limit per test2 secondsmemory limit per test256 megabytesinputstandard inputoutputstandard outputYou are given n elements numbered from 1 to n, the element i has value a_i and color c_i, initially, c_i = 0 for all i.The following operation can be applied:  Select three elements i, j and k (1 \leq i < j < k \leq n), such that c_i, c_j and c_k are all equal to 0 and a_i = a_k, then set c_j = 1. Find the maximum value of \sum\limits_{i=1}^n{c_i} that can be obtained after applying the given operation any number of times.InputThe first line contains an integer n (3 \leq n \leq 2 \cdot 10^5) — the number of elements.The second line consists of n integers a_1, a_2, \dots, a_n (1 \leq a_i \leq n), where a_i is the value of the i-th element.OutputPrint a single integer in a line — the maximum value of \sum\limits_{i=1}^n{c_i} that can be obtained after applying the given operation any number of times.ExamplesInput
7
1 2 1 2 7 4 7
Output
2
Input
13
1 2 3 2 1 3 3 4 5 5 5 4 7
Output
7
NoteIn the first test, it is possible to apply the following operations in order:  
7
1 2 1 2 7 4 7

2 
['dp', 'greedy', 'sortings', 'two pointers', '*2200']