#line 1 "main.cpp" /** * @title Template */ #include #include #include #include #include #include #include #line 2 "/Users/kodamankod/Desktop/Programming/Library/other/chmin_chmax.cpp" template constexpr bool chmin(T &lhs, const U &rhs) { if (lhs > rhs) { lhs = rhs; return true; } return false; } template constexpr bool chmax(T &lhs, const U &rhs) { if (lhs < rhs) { lhs = rhs; return true; } return false; } /** * @title Chmin/Chmax */ #line 2 "/Users/kodamankod/Desktop/Programming/Library/other/range.cpp" #line 4 "/Users/kodamankod/Desktop/Programming/Library/other/range.cpp" class range { public: class iterator { private: int64_t M_position; public: constexpr iterator(int64_t position) noexcept: M_position(position) { } constexpr void operator ++ () noexcept { ++M_position; } constexpr bool operator != (iterator other) const noexcept { return M_position != other.M_position; } constexpr int64_t operator * () const noexcept { return M_position; } }; class reverse_iterator { private: int64_t M_position; public: constexpr reverse_iterator(int64_t position) noexcept: M_position(position) { } constexpr void operator ++ () noexcept { --M_position; } constexpr bool operator != (reverse_iterator other) const noexcept { return M_position != other.M_position; } constexpr int64_t operator * () const noexcept { return M_position; } }; private: const iterator M_first, M_last; public: constexpr range(int64_t first, int64_t last) noexcept: M_first(first), M_last(std::max(first, last)) { } constexpr iterator begin() const noexcept { return M_first; } constexpr iterator end() const noexcept { return M_last; } constexpr reverse_iterator rbegin() const noexcept { return reverse_iterator(*M_last - 1); } constexpr reverse_iterator rend() const noexcept { return reverse_iterator(*M_first - 1); } }; /** * @title Range */ #line 2 "/Users/kodamankod/Desktop/Programming/Library/other/rev.cpp" #include #include #line 6 "/Users/kodamankod/Desktop/Programming/Library/other/rev.cpp" template class rev_impl { public: using iterator = decltype(std::rbegin(std::declval())); private: const iterator M_begin; const iterator M_end; public: constexpr rev_impl(T &&cont) noexcept: M_begin(std::rbegin(cont)), M_end(std::rend(cont)) { } constexpr iterator begin() const noexcept { return M_begin; } constexpr iterator end() const noexcept { return M_end; } }; template constexpr decltype(auto) rev(T &&cont) { return rev_impl(std::forward(cont)); } /** * @title Reverser */ #line 17 "main.cpp" using i32 = int32_t; using i64 = int64_t; using u32 = uint32_t; using u64 = uint64_t; constexpr i32 inf32 = (i32(1) << 30) - 1; constexpr i64 inf64 = (i64(1) << 62) - 1; std::vector lis(const std::vector &A) { const size_t N = A.size(); std::vector dp(N + 1, inf32); dp[0] = -inf32; std::vector res(N); for (auto i: range(0, N)) { chmin(*std::lower_bound(dp.begin(), dp.end(), A[i]), A[i]); res[i] = std::lower_bound(dp.begin(), dp.end(), inf32) - dp.begin() - 1; } return res; } i32 solve(std::vector A) { const size_t N = A.size(); const auto left = lis(A); std::reverse(A.begin(), A.end()); const auto right = lis(A); i32 res = 0; for (auto i: range(0, N)) { chmax(res, std::min(left[i], right[N - i - 1]) - 1); } return res; } int main() { size_t N; std::cin >> N; std::vector A(N); for (auto &x: A) { std::cin >> x; } i32 ans = solve(A); for (auto &x: A) { x = -x; } chmax(ans, solve(std::move(A))); std::cout << ans << '\n'; return 0; }