#include #define rep(i,a,b) for(int i=a;i=b;i--) #define fore(i,a) for(auto &i:a) #define all(x) (x).begin(),(x).end() //#pragma GCC optimize ("-O3") using namespace std; void _main(); int main() { cin.tie(0); ios::sync_with_stdio(false); _main(); } typedef long long ll; const int inf = INT_MAX / 2; const ll infl = 1LL << 60; templatebool chmax(T& a, const T& b) { if (a < b) { a = b; return 1; } return 0; } templatebool chmin(T& a, const T& b) { if (b < a) { a = b; return 1; } return 0; } //--------------------------------------------------------------------------------------------------- vector compress1(int *v, int n) { vector dic; rep(i, 0, n) dic.push_back(v[i]); sort(all(dic)); dic.erase(unique(all(dic)), dic.end()); rep(i, 0, n) v[i] = lower_bound(all(dic), v[i]) - dic.begin(); return dic; } #define def 0 template struct SegTree { //[l,r) V comp(V& l, V& r) { return max(l, r); }; vector val; SegTree() { val = vector(NV * 2, def); } V get(int x, int y, int l = 0, int r = NV, int k = 1) { if (r <= x || y <= l)return def; if (x <= l && r <= y)return val[k]; auto a = get(x, y, l, (l + r) / 2, k * 2); auto b = get(x, y, (l + r) / 2, r, k * 2 + 1); return comp(a, b); } void update(int i, V v) { i += NV; val[i] = v; while (i > 1) i >>= 1, val[i] = comp(val[i * 2], val[i * 2 + 1]); } void add(int i, V v) { update(i, val[i + NV] + v); } V operator[](int x) { return get(x, x + 1); } }; /*---------------------------------------------------------------------------------------------------             ∧_∧       ∧_∧  (´<_` )  Welcome to My Coding Space!      ( ´_ゝ`) /  ⌒i @hamayanhamayan0     /   \    | |     /   / ̄ ̄ ̄ ̄/  |   __(__ニつ/  _/ .| .|____      \/____/ (u ⊃ ---------------------------------------------------------------------------------------------------*/ int N, _A[101010], A[101010]; //--------------------------------------------------------------------------------------------------- SegTree st; int lft[101010], rht[101010]; int solve() { compress1(A, N); rep(i, 0, N) lft[i] = rht[i] = 0; rep(i, 0, N) st.update(i, 0); rep(i, 0, N) { chmax(lft[i], st.get(0, A[i]) + 1); st.update(A[i], max(st[A[i]], lft[i])); } rep(i, 0, N) st.update(i, 0); rrep(i, N - 1, 0) { chmax(rht[i], st.get(0, A[i]) + 1); st.update(A[i], max(st[A[i]], rht[i])); } int ans = 0; rep(i, 0, N) chmax(ans, min(lft[i], rht[i]) - 1); return ans; } //--------------------------------------------------------------------------------------------------- void _main() { cin >> N; rep(i, 0, N) cin >> _A[i]; int ans = 0; rep(i, 0, N) A[i] = _A[i]; chmax(ans, solve()); rep(i, 0, N) A[i] = -_A[i]; chmax(ans, solve()); cout << ans << endl; }