#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
#define MASK(x) (1LL << (x))
#define BIT(x, i) (((x) >> (i)) & 1)
#define ALL(x) (x).begin(), (x).end()
#define REP(i, n) for (int i = 0, _n = n; i < _n; ++i)
#define FOR(i, a, b) for (int i = (a), _b = (b); i <= _b; ++i)
#define FORD(i, a, b) for (int i = (a), _b = (b); i >= _b; --i)
#define FORE(i, a, b) for (int i = (a), _b = (b); i < _b; ++i)
#define debug(...) "[" << #__VA_ARGS__ ": " << (__VA_ARGS__) << "] "
#define file(name) if (fopen(name".inp", "r")) { freopen(name".inp", "r", stdin); freopen(name".out", "w", stdout); }
template <class A, class B> bool minimize(A &a, B b) { if (a > b) { a = b; return true; } return false; }
template <class A, class B> bool maximize(A &a, B b) { if (a < b) { a = b; return true; } return false; }
typedef tree <int, null_type, less_equal <int>, rb_tree_tag, tree_order_statistics_node_update> ordered_set;
int sub2 (int n, vector <int> a) {
int res = 0;
REP(l, n) {
unordered_map <int, int> cnt;
ordered_set values;
FORE(i, l, n) {
cnt[a[i]]++;
values.insert(a[i]);
int k = i - l + 1;
if(k % 2 == 0) {
res = max(res, cnt[*values.find_by_order(k / 2 - 1)]);
res = max(res, cnt[*values.find_by_order(k / 2)]);
} else {
res = max(res, cnt[*values.find_by_order(k / 2)]);
}
}
}
return res;
}
int sub3 (int n, vector <int> a) {
unordered_map <int, vector <pair <int, int>>> pos;
for (int l = 0; l < n;) {
int r = l;
while(r < n and a[r] == a[l]) ++r;
pos[a[l]].emplace_back(l, r - 1);
l = r;
}
auto is_median = [&] (int less, int greater, int equal) -> bool {
return (equal >= greater ? true : (equal + less >= greater));
};
int ans = 0;
for (auto [_, p] : pos) {
for (auto [l, r] : p) ans = max(ans, r - l + 1);
if((int) p.size() < 2) continue;
assert((int) p.size() == 2);
int equal = p[0].second - p[0].first + 1 + p[1].second - p[1].first + 1;
int less = p[0].first + n - 1 - p[1].second;
int greater = p[1].first - p[0].second - 1;
if(is_median(less, greater, equal)) ans = max(ans, equal);
}
return ans;
}
int sequence(int n, vector <int> a) {
return sub3(n, a);
if(n <= 2000) return sub2(n, a);
}
#ifdef LOCAL
#include <cassert>
#include <cstdio>
#include <vector>
int main() {
int N;
freopen("TASK.inp", "r", stdin);
freopen("TASK.out", "w", stdout);
cin >> N;
std::vector<int> A(N);
for (int i = 0; i < N; ++i) {
cin >> A[i];
}
int result = sequence(N, A);
cout << result;
return 0;
}
#endif
// Dream it. Wish it. Do it.
