#include #define REP(i, n) for (int i = 0, REP_N_ = (n); i < REP_N_; ++i) #define ALL(x) std::begin(x), std::end(x) using i64 = long long; using u64 = unsigned long long; template inline int ssize(const T &a) { return (int)std::size(a); } template inline bool chmax(T &a, T b) { return a < b and ((a = std::move(b)), true); } template inline bool chmin(T &a, T b) { return a > b and ((a = std::move(b)), true); } template std::istream &operator>>(std::istream &is, std::vector &a) { for (auto &x : a) is >> x; return is; } template std::ostream &pprint(const Container &a, std::string_view sep = " ", std::string_view ends = "\n", std::ostream *os = nullptr) { if (os == nullptr) os = &std::cout; auto b = std::begin(a), e = std::end(a); for (auto it = std::begin(a); it != e; ++it) { if (it != b) *os << sep; *os << *it; } return *os << ends; } template struct is_iterable : std::false_type {}; template struct is_iterable())), decltype(std::end(std::declval()))>> : std::true_type {}; template ::value && !std::is_same::value && !std::is_same::value>> std::ostream &operator<<(std::ostream &os, const T &a) { return pprint(a, ", ", "", &(os << "{")) << "}"; } template std::ostream &operator<<(std::ostream &os, const std::pair &a) { return os << "(" << a.first << ", " << a.second << ")"; } #ifdef ENABLE_DEBUG template void pdebug(const T &value) { std::cerr << value; } template void pdebug(const T &value, const Ts &...args) { pdebug(value); std::cerr << ", "; pdebug(args...); } #define DEBUG(...) \ do { \ std::cerr << " \033[33m (L" << __LINE__ << ") "; \ std::cerr << #__VA_ARGS__ << ":\033[0m "; \ pdebug(__VA_ARGS__); \ std::cerr << std::endl; \ } while (0) #else #define pdebug(...) #define DEBUG(...) #endif using namespace std; template struct ModInt { constexpr ModInt(long long val = 0) : _v(0) { if (val < 0) { long long k = (abs(val) + M - 1) / M; val += k * M; } assert(val >= 0); _v = val % M; } static constexpr int mod() { return M; } static constexpr unsigned int umod() { return M; } inline unsigned int val() const { return _v; } ModInt &operator++() { _v++; if (_v == umod()) _v = 0; return *this; } ModInt &operator--() { if (_v == 0) _v = umod(); _v--; return *this; } ModInt operator++(int) { auto result = *this; ++*this; return result; } ModInt operator--(int) { auto result = *this; --*this; return result; } constexpr ModInt operator-() const { return ModInt(-_v); } constexpr ModInt &operator+=(const ModInt &a) { if ((_v += a._v) >= M) _v -= M; return *this; } constexpr ModInt &operator-=(const ModInt &a) { if ((_v += M - a._v) >= M) _v -= M; return *this; } constexpr ModInt &operator*=(const ModInt &a) { _v = ((unsigned long long)(_v)*a._v) % M; return *this; } constexpr ModInt pow(unsigned long long t) const { ModInt base = *this; ModInt res = 1; while (t) { if (t & 1) res *= base; base *= base; t >>= 1; } return res; } constexpr ModInt inv() const { // Inverse by Extended Euclidean algorithm. // M doesn't need to be prime, but x and M must be coprime. assert(_v != 0); auto [g, x, y] = ext_gcd(_v, M); assert(g == 1LL); // The GCD must be 1. return x; // Inverse by Fermat's little theorem. // M must be prime. It's often faster. // // return pow(M - 2); } constexpr ModInt &operator/=(const ModInt &a) { return *this *= a.inv(); } friend constexpr ModInt operator+(const ModInt &a, const ModInt &b) { return ModInt(a) += b; } friend constexpr ModInt operator-(const ModInt &a, const ModInt &b) { return ModInt(a) -= b; } friend constexpr ModInt operator*(const ModInt &a, const ModInt &b) { return ModInt(a) *= b; } friend constexpr ModInt operator/(const ModInt &a, const ModInt &b) { return ModInt(a) /= b; } friend constexpr bool operator==(const ModInt &a, const ModInt &b) { return a._v == b._v; } friend constexpr bool operator!=(const ModInt &a, const ModInt &b) { return a._v != b._v; } friend std::istream &operator>>(std::istream &is, ModInt &a) { return is >> a._v; } friend std::ostream &operator<<(std::ostream &os, const ModInt &a) { return os << a._v; } private: // Extended Euclidean algorithm // Returns (gcd(a,b), x, y) where `a*x + b*y == gcd(a,b)`. static std::tuple ext_gcd(int a, int b) { int ax = 1, ay = 0, bx = 0, by = 1; for (;;) { if (b == 0) break; auto d = std::div(a, b); a = b; b = d.rem; ax -= bx * d.quot; std::swap(ax, bx); ay -= by * d.quot; std::swap(ay, by); } return {a, ax, ay}; } unsigned int _v; // raw value }; const unsigned int MOD = 998244353; using Mint = ModInt; template struct SegTree { using T = typename Monoid::T; inline int n() const { return n_; } inline int offset() const { return offset_; } explicit SegTree(int n) : n_(n) { offset_ = 1; while (offset_ < n_) offset_ <<= 1; data_.assign(2 * offset_, Monoid::id()); } explicit SegTree(const std::vector &leaves) : n_(leaves.size()) { offset_ = 1; while (offset_ < n_) offset_ <<= 1; data_.assign(2 * offset_, Monoid::id()); for (int i = 0; i < n_; ++i) { data_[offset_ + i] = leaves[i]; } for (int i = offset_ - 1; i > 0; --i) { data_[i] = Monoid::op(data_[i * 2], data_[i * 2 + 1]); } } // Sets i-th value (0-indexed) to x. void set(int i, const T &x) { int k = offset_ + i; data_[k] = x; // Update its ancestors. while (k > 1) { k >>= 1; data_[k] = Monoid::op(data_[k * 2], data_[k * 2 + 1]); } } // Queries by [l,r) range (0-indexed, half-open interval). T fold(int l, int r) const { l = std::max(l, 0) + offset_; r = std::min(r, offset_) + offset_; T vleft = Monoid::id(), vright = Monoid::id(); for (; l < r; l >>= 1, r >>= 1) { if (l & 1) vleft = Monoid::op(vleft, data_[l++]); if (r & 1) vright = Monoid::op(data_[--r], vright); } return Monoid::op(vleft, vright); } T fold_all() const { return data_[1]; } // Returns i-th value (0-indexed). T operator[](int i) const { return data_[offset_ + i]; } friend std::ostream &operator<<(std::ostream &os, const SegTree &st) { os << "["; for (int i = 0; i < st.n(); ++i) { if (i != 0) os << ", "; const auto &x = st[i]; os << x; } return os << "]"; } private: int n_; // number of valid leaves. int offset_; // where leaves start std::vector data_; // data size: 2*offset_ }; struct Sum { struct T { Mint sum; i64 count; }; static T op(const T &x, const T &y) { return {x.sum + y.sum, x.count + y.count}; } static constexpr T id() { return {0, 0}; } }; template struct Compress { std::vector vec; explicit Compress(std::vector v) : vec(v) { std::sort(vec.begin(), vec.end()); vec.erase(std::unique(vec.begin(), vec.end()), vec.end()); } int size() const { return vec.size(); } int index(T x) const { return lower_bound(vec.begin(), vec.end(), x) - vec.begin(); } const T &value(int i) const { return vec[i]; } }; Mint solve() { int N; cin >> N; vector A(N); cin >> A; Compress ca(A); SegTree seg(ca.size()), seg2(ca.size()); Mint ans = 0; for (int i = N - 1; i >= 0; --i) { int j = ca.index(A[i]); auto r2 = seg2.fold(0, j); ans += r2.sum + r2.count * Mint(A[i]); { auto qj = seg[j]; qj.sum += A[i]; qj.count++; seg.set(j, qj); } auto r1 = seg.fold(0, j); Mint sum2 = r1.sum + r1.count * Mint(A[i]); i64 count2 = r1.count; if (count2 > 0) { auto qj = seg2[j]; qj.sum += sum2; qj.count += count2; seg2.set(j, qj); } } return ans; } int main() { ios::sync_with_stdio(false); cin.tie(nullptr); cout << solve() << endl; }