#include using namespace std; template struct segtree { public: segtree() : segtree(0) {} segtree(int n) : segtree(std::vector(n, e())) {} segtree(const std::vector& v) : _n(int(v.size())) { log = ceil_pow2(_n); size = 1 << log; d = std::vector(2 * size, e()); for (int i = 0; i < _n; i++) d[size + i] = v[i]; for (int i = size - 1; i >= 1; i--) { update(i); } } void set(int p, S x) { assert(0 <= p && p < _n); p += size; d[p] = x; for (int i = 1; i <= log; i++) update(p >> i); } S get(int p) { assert(0 <= p && p < _n); return d[p + size]; } const S operator[](int p) const { return get(p); } S operator[](int p) { return get(p); } S prod(int l, int r) { assert(0 <= l && l <= r && r <= _n); S sml = e(), smr = e(); l += size; r += size; while (l < r) { if (l & 1) sml = op(sml, d[l++]); if (r & 1) smr = op(d[--r], smr); l >>= 1; r >>= 1; } return op(sml, smr); } S all_prod() { return d[1]; } template int max_right(int l) { return max_right(l, [](S x) { return f(x); }); } template int max_right(int l, F f) { assert(0 <= l && l <= _n); assert(f(e())); if (l == _n) return _n; l += size; S sm = e(); do { while (l % 2 == 0) l >>= 1; if (!f(op(sm, d[l]))) { while (l < size) { l = (2 * l); if (f(op(sm, d[l]))) { sm = op(sm, d[l]); l++; } } return l - size; } sm = op(sm, d[l]); l++; } while ((l & -l) != l); return _n; } template int min_left(int r) { return min_left(r, [](S x) { return f(x); }); } template int min_left(int r, F f) { assert(0 <= r && r <= _n); assert(f(e())); if (r == 0) return 0; r += size; S sm = e(); do { r--; while (r > 1 && (r % 2)) r >>= 1; if (!f(op(d[r], sm))) { while (r < size) { r = (2 * r + 1); if (f(op(d[r], sm))) { sm = op(d[r], sm); r--; } } return r + 1 - size; } sm = op(d[r], sm); } while ((r & -r) != r); return 0; } private: int _n, size, log; std::vector d; int ceil_pow2(int n) { int x = 0; while ((1U << x) < (unsigned int)(n)) x++; return x; } void update(int k) { d[k] = op(d[2 * k], d[2 * k + 1]); } }; int op(int lhs, int rhs){return max(lhs, rhs);} int e(){return 0;} int main(){ ios::sync_with_stdio(false); cin.tie(0); int N, ans = 0; cin >> N; vector a(N), c, L(N), R(N); for(int i = 0; i < N; i++)cin >> a[i]; c = a; sort(c.begin(), c.end()); c.erase(unique(c.begin(), c.end()), c.end()); for(int i = 0; i < N; i++)a[i] = lower_bound(c.begin(), c.end(), a[i]) - c.begin(); segtree seg(c.size()); for(int i = 0; i < N; i++){ L[i] = seg.prod(a[i] + 1, c.size()); seg.set(a[i], L[i] + 1); } seg = segtree(c.size()); for(int i = N - 1; i >= 0; i--){ R[i] = seg.prod(a[i] + 1, c.size()); seg.set(a[i], R[i] + 1); ans = max(ans, min(L[i], R[i])); } seg = segtree(c.size()); for(int i = 0; i < N; i++){ L[i] = seg.prod(0, a[i]); seg.set(a[i], L[i] + 1); } seg = segtree(c.size()); for(int i = N - 1; i >= 0; i--){ R[i] = seg.prod(0, a[i]); seg.set(a[i], R[i] + 1); ans = max(ans, min(L[i], R[i])); } cout << ans << '\n'; }