#include<iostream>
#include<string>
#include<cstdio>
#include<vector>
#include<cmath>
#include<algorithm>
#include<functional>
#include<iomanip>
#include<queue>
#include<ciso646>
#include<random>
#include<map>
#include<set>
#include<bitset>
#include<stack>
#include<unordered_map>
#include<utility>
#include<cassert>
#include<complex>
#include<numeric>
#include<array>
using namespace std;

//#define int long long
typedef long long ll;

typedef unsigned long long ul;
typedef unsigned int ui;
constexpr ll mod = 1000000007;
const ll INF = mod * mod;
typedef pair<int, int>P;
#define stop char nyaa;cin>>nyaa;
#define rep(i,n) for(int i=0;i<n;i++)
#define per(i,n) for(int i=n-1;i>=0;i--)
#define Rep(i,sta,n) for(int i=sta;i<n;i++)
#define rep1(i,n) for(int i=1;i<=n;i++)
#define per1(i,n) for(int i=n;i>=1;i--)
#define Rep1(i,sta,n) for(int i=sta;i<=n;i++)
#define all(v) (v).begin(),(v).end()
typedef pair<ll, ll> LP;
typedef double ld;
typedef pair<ld, ld> LDP;
const ld eps = 1e-12;
const ld pi = acos(-1.0);

ll mod_pow(ll x, ll n, ll m) {
	ll res = 1;
	while (n) {
		if (n & 1)res = res * x % m;
		x = x * x % m; n >>= 1;
	}
	return res;
}
struct modint {
	ll n;
	modint() :n(0) { ; }
	modint(ll m) :n(m) {
		if (n >= mod)n %= mod;
		else if (n < 0)n = (n % mod + mod) % mod;
	}
	operator int() { return n; }
};
bool operator==(modint a, modint b) { return a.n == b.n; }
modint operator+=(modint& a, modint b) { a.n += b.n; if (a.n >= mod)a.n -= mod; return a; }
modint operator-=(modint& a, modint b) { a.n -= b.n; if (a.n < 0)a.n += mod; return a; }
modint operator*=(modint& a, modint b) { a.n = ((ll)a.n * b.n) % mod; return a; }
modint operator+(modint a, modint b) { return a += b; }
modint operator-(modint a, modint b) { return a -= b; }
modint operator*(modint a, modint b) { return a *= b; }
modint operator^(modint a, ll n) {
	if (n == 0)return modint(1);
	modint res = (a * a) ^ (n / 2);
	if (n % 2)res = res * a;
	return res;
}

ll inv(ll a, ll p) {
	return (a == 1 ? 1 : (1 - p * inv(p % a, a)) / a + p);
}
modint operator/(modint a, modint b) { return a * modint(inv(b, mod)); }

const int max_n = 1 << 2;
modint fact[max_n], factinv[max_n];
void init_f() {
	fact[0] = modint(1);
	for (int i = 0; i < max_n - 1; i++) {
		fact[i + 1] = fact[i] * modint(i + 1);
	}
	factinv[max_n - 1] = modint(1) / fact[max_n - 1];
	for (int i = max_n - 2; i >= 0; i--) {
		factinv[i] = factinv[i + 1] * modint(i + 1);
	}
}
modint comb(int a, int b) {
	if (a < 0 || b < 0 || a < b)return 0;
	return fact[a] * factinv[b] * factinv[a - b];
}

ll gcd(ll a, ll b) {
	if (a < b)swap(a, b);
	while (b) {
		ll r = a % b; a = b; b = r;
	}
	return a;
}

const int b = 4;
struct ste {
	int val, pre, id;
};
bool operator==(ste const& a, ste const& b){
	return a.id == b.id && a.val == b.val && a.pre == b.pre;
}


struct SegT {
private:
	int sz; vector<array<ste,4>> node;
	const array<ste, 4> init_c = { ste{0,-1,-1},ste{0,-1,-1},ste{0,-1,-1},ste{0,-1,-1} };
public:
	SegT(int n) {
		sz = 1;
		while (sz < n)sz *= 2;
		node.resize(2 * sz - 1, init_c);
	}
	array<ste,4> f(array<ste,4> a, array<ste,4>b) {
		array<ste, 8> res;
		int tmp = 0;
		int id1 = 0, id2 = 0;
		rep(i, a.size()+b.size()) {
			if (id1 == a.size()) {
				res[tmp] = b[id2];
				id2++; tmp++;
			}
			else if (id2 == b.size()) {
				res[tmp] = a[id1]; tmp++; id1++;
			}
			else {
				if (a[id1].val > b[id2].val) {
					res[tmp] = a[id1]; tmp++; id1++;
				}
				else {
					res[tmp] = b[id2];
					id2++; tmp++;
				}
			}
		}
		array<ste, 4> tres = init_c;
		tmp = 0;
		for (ste s : res) {
			bool valid = true;
			int c0 = 0, c1 = 0;
			rep(j, tmp) {
				if (tres[j].pre == s.pre && tres[j].id == s.id) {
					valid = false; break;
				}
				if (tres[j].pre == s.pre)c0++;
				if (tres[j].id == s.id)c1++;
			}
			if (c0 >= 2 || c1 >= 2)valid = false;
			if (valid) {
				tres[tmp] = s; tmp++; if (tmp == 4)break;
			}
		}
		return tres;
	}
	void update(int k, array<ste,4> a) {
		k += sz - 1;
		node[k] = f(node[k],a);
		while (k > 0) {
			k = (k - 1) / 2;
			node[k] = f(node[k * 2 + 1], node[k * 2 + 2]);
		}
	}
	array<ste,4> query(int a, int b, int k = 0, int l = 0, int r = -1) {
		if (r < 0)r = sz;
		if (r <= a || b <= l)return init_c;
		else if (a <= l && r <= b)return node[k];
		else {
			array<ste,4> vl = query(a, b, k * 2 + 1, l, (l + r) / 2);
			array<ste,4> vr = query(a, b, k * 2 + 2, (l + r) / 2, r);
			return f(vl, vr);
		}
	}
};
void solve() {
	int n; cin >> n;
	int sz = 1 << 20;
	SegT up(sz), dw(sz);
	vector<int> a(n);
	rep(i, n)cin >> a[i];
	rep(i, n) {
		array<ste,4> x = dw.query(a[i] + 1, sz);
		array<ste, 4> nw; rep(i, 4)nw[i] = { 0,-1,-1 };
		int tmp = 0;
		for (ste s : x) {
			if (s.pre == a[i])continue;
			int v = s.val + 1;
			int p = s.id;
			int id = a[i];
			nw[tmp] = { v,p,id }; tmp++;
		}
		up.update(a[i], nw);
		x = up.query(0, a[i]);
		rep(i, 4)nw[i] = { 0,-1,-1 };
		tmp = 0;
		for (ste s : x) {
			if (s.pre == a[i])continue;
			int v = s.val + 1;
			int p = s.id;
			int id = a[i];
			nw[tmp] = { v,p,id }; tmp++;
		}
		dw.update(a[i], nw);
	}
	int ans = 0;
	array<ste,4> s = up.query(0, sz);
	ans = max(ans, s[0].val);
	s = dw.query(0, sz);
	ans = max(ans, s[0].val);
	if (ans < 3)ans = 0;
	cout << ans << "\n";
}

signed main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	//cout << fixed << setprecision(10);
	//init_f();
	//expr();
	//int t; cin >> t; rep(i, t)
	//while (cin >> n >> m>>s1>>s2>>t, n)
	solve();
	return 0;
}