#include <bits/stdc++.h>
#include "sequence.h"
#define isz(x) (int)x.size()
using namespace std;

template<bool HAS_QUERY, bool HAS_UPDATE, class T, class U, class F1, class F2, class F3>
struct segment_tree_base{
	static_assert(HAS_QUERY || HAS_UPDATE);
#define ifQ if constexpr(HAS_QUERY)
#define ifU if constexpr(HAS_UPDATE)
	int n, size, log;
	vector<T> data;
	vector<U> data_action;
	F1 TT; // monoid operation (always adjacent)
	T T_id; // monoid identity
	F2 UU; // monoid operation (superset, subset)
	U U_id; // monoid identity
	F3 UT; // action of U on T (superset, subset)
	// O(n)
	segment_tree_base(F1 TT, T T_id, F2 UU, U U_id, F3 UT): TT(TT), T_id(T_id), UU(UU), U_id(U_id), UT(UT){ }
	segment_tree_base &operator=(const segment_tree_base &seg){
		n = seg.n;
		size = seg.size;
		log = seg.log;
		data = seg.data;
		data_action = seg.data_action;
	}
	// O(1)
	friend void swap(segment_tree_base &x, segment_tree_base &y){
		swap(x.n, y.n);
		swap(x.size, y.size);
		swap(x.log, y.log);
		swap(x.data, y.data);
		swap(x.data_action, y.data_action);
	}
	// O(n)
	void build(int n){
		assert(n >= 0);
		this->n = n;
		size = 1;
		while(size < n) size <<= 1;
		log = __lg(size);
		ifQ data.assign(size << 1, T_id);
		ifU data_action.assign(HAS_QUERY ? size : size << 1, U_id);
	}
	// O(n)
	void build(int n, T x){
		static_assert(HAS_QUERY);
		assert(n >= 0);
		this->n = n;
		size = 1;
		while(size < n) size <<= 1;
		log = __lg(size);
		data.assign(size << 1, T_id);
		fill(data.begin() + size, data.begin() + size + n, x);
		for(auto i = size - 1; i >= 1; -- i) refresh(i);
		ifU data_action.assign(size, U_id);
	}
	// O(n)
	template<class V>
	void build(const vector<V> &a){
		static_assert(HAS_QUERY);
		n = (int)a.size();
		size = 1;
		while(size < n) size <<= 1;
		log = __lg(size);
		data.assign(size << 1, T_id);
		copy(a.begin(), a.end(), data.begin() + size);
		for(auto i = size - 1; i >= 1; -- i) refresh(i);
		ifU data_action.assign(size, U_id);
	}
	// O(n)
	void build_action(int n){
		static_assert(!HAS_QUERY && HAS_UPDATE);
		assert(n >= 0);
		build(n);
	}
	// O(n)
	void build_action(int n, U f){
		static_assert(!HAS_QUERY && HAS_UPDATE);
		assert(n >= 0);
		this->n = n;
		size = 1;
		while(size < n) size <<= 1;
		log = __lg(size);
		data_action.assign(size << 1, U_id);
		fill(data_action.begin() + size, data_action.begin() + size + n, f);
	}
	// O(n)
	template<class V>
	void build_action(const vector<V> &a){
		static_assert(!HAS_QUERY && HAS_UPDATE);
		n = (int)a.size();
		size = 1;
		while(size < n) size <<= 1;
		log = __lg(size);
		data_action.assign(size << 1, U_id);
		copy(a.begin(), a.end(), data_action.begin() + size);
	}
	// O(1)
	void refresh(int u){
		static_assert(HAS_QUERY);
		data[u] = TT(data[u << 1], data[u << 1 | 1]);
	}
	// O(1)
	void apply(int u, U f){
		static_assert(HAS_UPDATE);
		ifQ data[u] = UT(f, data[u]);
		if(!HAS_QUERY || u < size) data_action[u] = UU(f, data_action[u]);
	}
	// O(1)
	void push(int u){
		static_assert(HAS_UPDATE);
		apply(u << 1, data_action[u]), apply(u << 1 | 1, data_action[u]);
		data_action[u] = U_id;
	}
	// O(log(n)) if HAS_UPDATE, O(1) otherwise.
	T query(int p){
		static_assert(HAS_QUERY);
		assert(0 <= p && p < n);
		p += size;
		ifU for(auto i = log; i >= 1; -- i) push(p >> i);
		return data[p];
	}
	// O(log(n))
	U query_action(int p){
		static_assert(!HAS_QUERY && HAS_UPDATE);
		assert(0 <= p && p < n);
		p += size;
		ifU for(auto i = log; i >= 1; -- i) push(p >> i);
		return data_action[p];
	}
	// O(log(n))
	T query(int ql, int qr){
		static_assert(HAS_QUERY);
		assert(0 <= ql && ql <= qr && qr <= n);
		if(ql == qr) return T_id;
		ql += size, qr += size;
		ifU for(auto i = log; i >= 1; -- i){
			if(ql >> i << i != ql) push(ql >> i);
			if(qr >> i << i != qr) push(qr >> i);
		}
		T res_left = T_id, res_right = T_id;
		for(; ql < qr; ql >>= 1, qr >>= 1){
			if(ql & 1) res_left = TT(res_left, data[ql ++]);
			if(qr & 1) res_right = TT(data[-- qr], res_right);
		}
		return TT(res_left, res_right);
	}
	// O(1)
	T query_all() const{
		static_assert(HAS_QUERY);
		return data[1];
	}
	// O(n)
	vector<T> to_array(){
		static_assert(HAS_QUERY);
		ifU for(auto u = 1; u < size; ++ u) push(u);
		return vector<T>(data.begin() + size, data.begin() + size + n);
	}
	// O(n)
	vector<U> to_array_of_updates(){
		static_assert(!HAS_QUERY && HAS_UPDATE);
		for(auto u = 1; u < size; ++ u) push(u);
		return vector<U>(data_action.begin() + size, data_action.begin() + size + n);
	}
	// O(log(n))
	void set(int p, T x){
		static_assert(HAS_QUERY);
		assert(0 <= p && p < n);
		p += size;
		ifU for(auto i = log; i >= 1; -- i) push(p >> i);
		data[p] = x;
		for(auto i = 1; i <= log; ++ i) refresh(p >> i);
	}
	// O(log(n))
	void set_action(int p, U f){
		static_assert(!HAS_QUERY && HAS_UPDATE);
		assert(0 <= p && p < n);
		p += size;
		for(auto i = log; i >= 1; -- i) push(p >> i);
		data_action[p] = f;
	}
	// O(log(n))
	void update(int p, U f){
		static_assert(HAS_UPDATE);
		assert(0 <= p && p < n);
		p += size;
		for(auto i = log; i >= 1; -- i) push(p >> i);
		ifQ{
			data[p] = UT(f, data[p]);
			for(auto i = 1; i <= log; ++ i) refresh(p >> i);
		}
		else data_action[p] = UU(f, data_action[p]);
	}
	// O(log(n))
	void update(int ql, int qr, U f){
		static_assert(HAS_UPDATE);
		assert(0 <= ql && ql <= qr && qr <= n);
		if(ql == qr) return;
		ql += size, qr += size;
		for(auto i = log; i >= 1; -- i){
			if(ql >> i << i != ql) push(ql >> i);
			if(qr >> i << i != qr) push(qr >> i);
		}
		int _ql = ql, _qr = qr;
		for(; ql < qr; ql >>= 1, qr >>= 1){
			if(ql & 1) apply(ql ++, f);
			if(qr & 1) apply(-- qr, f);
		}
		ql = _ql, qr = _qr;
		ifQ for(auto i = 1; i <= log; ++ i){
			if(ql >> i << i != ql) refresh(ql >> i);
			if(qr >> i << i != qr) refresh(qr >> i);
		}
	}
	void update_beats(int ql, int qr, auto exit_rule, auto enter_rule, auto update_rule){
		static_assert(HAS_QUERY && HAS_UPDATE);
		assert(0 <= ql && ql <= qr && qr <= n);
		if(ql == qr) return;
		ql += size, qr += size;
		for(auto i = log; i >= 1; -- i){
			if(ql >> i << i != ql) push(ql >> i);
			if(qr >> i << i != qr) push(qr >> i);
		}
		auto recurse = [&](auto self, int u)->void{
			if(exit_rule(data[u])) return;
			if(enter_rule(data[u])){
				apply(u, update_rule(data[u]));
				return;
			}
			push(u);
			self(self, u << 1), self(self, u << 1 | 1);
			refresh(u);
		};
		int _ql = ql, _qr = qr;
		for(; ql < qr; ql >>= 1, qr >>= 1){
			if(ql & 1) recurse(recurse, ql ++);
			if(qr & 1) recurse(recurse, -- qr);
		}
		ql = _ql, qr = _qr;
		for(auto i = 1; i <= log; ++ i){
			if(ql >> i << i != ql) refresh(ql >> i);
			if(qr >> i << i != qr) refresh(qr >> i);
		}
	}
	// pred(sum[ql, r)) is T, T, ..., T, F, F, ..., F
	// Returns max r with T
	// O(log(n))
	int max_pref(int ql, auto pred){
		static_assert(HAS_QUERY);
		assert(0 <= ql && ql <= n && pred(T_id));
		if(ql == n) return n;
		ql += size;
		ifU for(auto i = log; i >= 1; -- i) push(ql >> i);
		T sum = T_id;
		do{
			while(~ql & 1) ql >>= 1;
			if(!pred(TT(sum, data[ql]))){
				while(ql < size){
					ifU push(ql);
					ql = ql << 1;
					if(pred(TT(sum, data[ql]))) sum = TT(sum, data[ql ++]);
				}
				return ql - size;
			}
			sum = TT(sum, data[ql]);
			++ ql;
		}while((ql & -ql) != ql);
		return n;
	}
	// pred(sum[l, qr)) is F, F, ..., F, T, T, ..., T
	// Returns min l with T
	// O(log(n))
	int min_suff(int qr, auto pred){
		static_assert(HAS_QUERY);
		assert(0 <= qr && qr <= n && pred(T_id));
		if(qr == 0) return 0;
		qr += size;
		ifU for(auto i = log; i >= 1; -- i) push(qr - 1 >> i);
		T sum = T_id;
		do{
			-- qr;
			while(qr > 1 && qr & 1) qr >>= 1;
			if(!pred(TT(data[qr], sum))){
				while(qr < size){
					ifU push(qr);
					qr = qr << 1 | 1;
					if(pred(TT(data[qr], sum))) sum = TT(data[qr --], sum);
				}
				return qr + 1 - size;
			}
			sum = TT(data[qr], sum);
		}while((qr & -qr) != qr);
		return 0;
	}
	template<class output_stream>
	friend output_stream &operator<<(output_stream &out, segment_tree_base<HAS_QUERY, HAS_UPDATE, T, U, F1, F2, F3> seg){
		out << "{";
		for(auto i = 0; i < seg.n; ++ i){
			ifQ out << seg.query(i);
			else out << seg.query_action(i);
			if(i != seg.n - 1) out << ", ";
		}
		return out << '}';
	}
#undef ifQ
#undef ifU
};

// Supports query
template<class T, class F>
auto make_Q_segment_tree(F TT, T T_id){
	using U = int;
	auto _UU = [&](U, U)->U{ return U{}; };
	auto _UT = [&](U, T)->T{ return T{}; };
	return segment_tree_base<true, false, T, U, F, decltype(_UU), decltype(_UT)>(TT, T_id, _UU, U{}, _UT);
}
// Supports update
template<class U, class F>
auto make_U_segment_tree(F UU, U U_id){
	using T = int;
	auto _TT = [&](T, T)->T{ return T{}; };
	auto _UT = [&](U, T)->T{ return T{}; };
	return segment_tree_base<false, true, T, U, decltype(_TT), F, decltype(_UT)>(_TT, T{}, UU, U_id, _UT);
}
// Supports query and update
template<class T, class U, class F1, class F2, class F3>
auto make_QU_segment_tree(F1 TT, T T_id, F2 UU, U U_id, F3 UT){
	return segment_tree_base<true, true, T, U, F1, F2, F3>(TT, T_id, UU, U_id, UT);
}

struct node {
	int mx = 0;
	int mn = INT_MAX;

	node() {}
	node(int val) : mx(val), mn(val) {}
};

struct lz_node {
	int lz = 0;
	lz_node() {}
	lz_node(int val) : lz(val) {}
};

node op1(node a, node b) {
	node res;
	res.mn = min(a.mn, b.mn);
	res.mx = max(a.mx, b.mx);
	return res;
}

node op2(lz_node a, node b) {
	node res;
	res.mn = b.mn + a.lz;
	res.mx = b.mx + a.lz;
	return res;
}

lz_node op3(lz_node a, lz_node b) {
	lz_node res;
	res.lz = a.lz + b.lz;
	return res;
}

int sequence(int n, vector<int> a) {
	vector<vector<int>> ap(n);
	for (int i = 0; i < n; ++i) {
		a[i]--;
		ap[a[i]].emplace_back(i);
	}

	auto st = make_QU_segment_tree(op1, node(), op3, lz_node(), op2);
	st.build(n + 1, node(0));

	for (int i = 0; i < n; ++i) st.update(i + 1, n + 1, lz_node(1));

	int res = 0;
	vector<int> pfx_mn(n);
	vector<int> pfx_mx(n);
	vector<int> sfx_mn(n);
	vector<int> sfx_mx(n);
	for (int i = 0; i < n; ++i) {
		for (int idx : ap[i]) {
			pfx_mn[idx] = st.query(0, idx + 1).mn;
			sfx_mx[idx] = st.query(idx + 1, n + 1).mx;
		}
		for (int idx : ap[i]) st.update(idx + 1, n + 1, lz_node(-2));
		for (int idx : ap[i]) {
			pfx_mx[idx] = st.query(0, idx + 1).mx;
			sfx_mn[idx] = st.query(idx + 1, n + 1).mn;
		}

		int ptr = 0;
		vector<int> vec;
		for (int idx : ap[i]) {
			vec.emplace_back(idx);
			while (ptr < isz(vec) and 1ll * (sfx_mx[idx] - pfx_mn[vec[ptr]]) * (sfx_mn[idx] - pfx_mx[vec[ptr]]) > 0) ++ptr;
			res = max(res, isz(vec) - ptr);
			// cout << i << " " << idx << " " << isz(vec) - ptr << endl;
			// cout << idx << " " << sfx_mx[idx] << " " << sfx_mn[idx] << endl;
			// cout << vec[ptr] << " " << pfx_mx[vec[ptr]] << " " << pfx_mn[vec[ptr]] << endl;
		}
	}

	return res;
}