#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include 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 pairP; #define stop char nyaa;cin>>nyaa; #define rep(i,n) for(int i=0;i=0;i--) #define Rep(i,sta,n) for(int i=sta;i=1;i--) #define Rep1(i,sta,n) for(int i=sta;i<=n;i++) #define all(v) (v).begin(),(v).end() typedef pair LP; typedef double ld; typedef pair 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> node; const vector init_c=vector(b, ste{0,-1,-1}); public: SegT(int n) { sz = 1; while (sz < n)sz *= 2; node.resize(2 * sz - 1, init_c); } vector f(vector a, vectorb) { vector res; int id1 = 0, id2 = 0; rep(i, 8) { if (id1 == 4) { res.push_back(b[id2]); id2++; } else if (id2 == 4) { res.push_back(a[id1]); id1++; } else { if (a[id1].val > b[id2].val) { res.push_back(a[id1]); id1++; } else { res.push_back(b[id2]); id2++; } } } vector tres; for (ste s : res) { bool valid = true; for (ste p : tres) { if (p.pre == s.pre && p.id == s.id) { valid = false; break; } } if (valid)tres.push_back(s); } tres.resize(4, { 0,-1,-1 }); return tres; } void update(int k, int v,int p,int id) { k += sz - 1; vector val(4, { 0,-1,-1 }); val[0] = { v,p,id }; vector cop = node[k]; node[k] = f(node[k],val); if (cop == node[k])return; while (k > 0) { k = (k - 1) / 2; node[k] = f(node[k * 2 + 1], node[k * 2 + 2]); } } vector 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 { vector vl = query(a, b, k * 2 + 1, l, (l + r) / 2); vector 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 a(n); rep(i, n)cin >> a[i]; rep(i, n) { vector x = dw.query(a[i] + 1, sz); for (ste s : x) { if (s.pre == a[i])continue; int v = s.val + 1; int p = s.id; int id = a[i]; up.update(a[i], v, p, id); } x = up.query(0, a[i]); for (ste s : x) { if (s.pre == a[i])continue; int v = s.val + 1; int p = s.id; int id = a[i]; dw.update(a[i], v, p, id); } } int ans = 0; vector 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; }