#include "sequence.h"
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
using namespace std;
pair<int, int> mids(int sz) {
int m1 = sz / 2;
int m2 = sz / 2 + (sz % 2);
return {m1, m2};
}
int sequence(int N, std::vector<int> A) {
int res = 0;
vector<map<int, int>> p(A.size() + 1);
for (size_t i = 0; i < A.size(); ++i) {
for (auto [key, val]: p[i]) {
p[i + 1][key] = val;
}
p[i + 1][A[i]]++;
}
for (int l = 0; l < (int)A.size(); ++l) {
tree<pair<int, int>, null_type, less<pair<int, int>>, rb_tree_tag, tree_order_statistics_node_update> st;
for (int r = l; r < (int)A.size(); ++r) {
st.insert(pair{A[r], r});
auto [m1, m2] = mids(st.size() - 1);
m1 = st.find_by_order(m1)->first;
m2 = st.find_by_order(m2)->first;
res = max(res, max(p[r + 1][m1] - p[l][m1], p[r + 1][m2] - p[l][m2]));
}
}
return res;
}
