#include #define For(i, a, b) for (int(i) = (int)(a); (i) < (int)(b); ++(i)) #define rFor(i, a, b) for (int(i) = (int)(a)-1; (i) >= (int)(b); --(i)) #define rep(i, n) For((i), 0, (n)) #define rrep(i, n) rFor((i), (n), 0) #define fi first #define se second using namespace std; typedef long long lint; typedef unsigned long long ulint; typedef pair pii; typedef pair pll; template bool chmax(T &a, const T &b) { if (a < b) { a = b; return true; } return false; } template bool chmin(T &a, const T &b) { if (a > b) { a = b; return true; } return false; } template T div_floor(T a, T b) { if (b < 0) a *= -1, b *= -1; return a >= 0 ? a / b : (a + 1) / b - 1; } template T div_ceil(T a, T b) { if (b < 0) a *= -1, b *= -1; return a > 0 ? (a - 1) / b + 1 : a / b; } constexpr lint mod = 1000000007; constexpr lint INF = mod * mod; constexpr int MAX = 200010; template struct SegTree { int sz = 1, seq_sz; T et; F f; G g; vector node; SegTree(int sz_, T et, F f, G g) : seq_sz(sz_), et(et), f(f), g(g) { while (sz < sz_) sz <<= 1; node.resize(sz << 1, et); } void build(vector &a) { rep(i, a.size()) node[i + sz] = a[i]; rFor(i, sz, 1) node[i] = f(node[i << 1], node[(i << 1) + 1]); } void build(T x) { rep(i, seq_sz) node[i + sz] = x; rFor(i, sz, 1) node[i] = f(node[i << 1], node[(i << 1) + 1]); } void update(int i, E x) { i += sz; node[i] = g(node[i], x); i >>= 1; while (i) { node[i] = f(node[i << 1], node[(i << 1) + 1]); i >>= 1; } } T query(int l, int r) { T vl = et, vr = et; for (l += sz, r += sz; l < r; l >>= 1, r >>= 1) { if (l & 1) vl = f(vl, node[l++]); if (r & 1) vr = f(node[--r], vr); } return f(vl, vr); } int search_left(int l, const T val, function cmp, function check) { T sum = et; for (l += sz;; l >>= 1) { if (check(f(sum, node[l]), val)) { while (l < sz) { if (check(f(sum, node[l << 1]), val)) l <<= 1; else { sum = f(sum, node[l << 1]); l = (l << 1) + 1; } } return l - sz; } if (__builtin_popcount(l + 1) == 1) return seq_sz; if (l & 1) sum = f(sum, node[l++]); } } int search_right(int r, const T val, function cmp, function check) { T sum = et; for (r += sz;; r >>= 1) { if (check(f(sum, node[r]), val)) { while (r < sz) { if (check(f(node[(r << 1) + 1], sum), val)) r = (r << 1) + 1; else { sum = f(node[(r << 1) + 1], sum); r <<= 1; } } return r - sz; } if (__builtin_popcount(r) == 1) return -1; if (!(r & 1)) sum = f(node[r--], sum); } } int lower_bound_left(int l, const T val, function cmp = less<>()) { auto check = [&cmp](auto a, auto b) { return !cmp(a, b); }; return search_left(l, val, cmp, check); } int upper_bound_left(int l, const T val, function cmp = less<>()) { auto check = [&cmp](auto a, auto b) { return cmp(b, a); }; return search_left(l, val, cmp, check); } int lower_bound_right(int l, const T val, function cmp = greater<>()) { auto check = [&cmp](auto a, auto b) { return !cmp(b, a); }; return search_right(l, val, cmp, check); } int upper_bound_right(int l, const T val, function cmp = greater<>()) { auto check = [&cmp](auto a, auto b) { return cmp(a, b); }; return search_right(l, val, cmp, check); } }; vector v; int idx(int x) { return lower_bound(v.begin(), v.end(), x) - v.begin(); } int main() { int n; scanf("%d", &n); int a[n]; rep(i, n) { scanf("%d", &a[i]); v.push_back(a[i]); } sort(v.begin(), v.end()); v.erase(unique(v.begin(), v.end()), v.end()); auto f = [](int x, int y) { return max(x, y); }; SegTree st_f1(n, 0, f, f), st_f2(n, 0, f, f), st_b1(n, 0, f, f), st_b2(n, 0, f, f); int f1[n], f2[n], b1[n], b2[n]; rep(i, n) { int pos = idx(a[i]); f1[i] = st_f1.query(0, pos) + 1; f2[i] = st_f2.query(pos + 1, n) + 1; st_f1.update(pos, f1[i]); st_f2.update(pos, f2[i]); } rrep(i, n) { int pos = idx(a[i]); b1[i] = st_b1.query(0, pos) + 1; b2[i] = st_b2.query(pos + 1, n) + 1; st_b1.update(pos, b1[i]); st_b2.update(pos, b2[i]); } int ans = 0; rep(i, n) { chmax(ans, min(f1[i], b1[i]) - 1); chmax(ans, min(f2[i], b2[i]) - 1); } printf("%d\n", ans); }