#include #include namespace nono { template class FenwickTree { public: FenwickTree(int size = 0): size_(size), data_(size_ + 1) {} void add(int i, const T& v) { for (++i; i <= size_; i += i & -i) { data_[i] += v; } } T sum(int i) const { T result{}; for (; i > 0; i -= i & -i) { result += data_[i]; } return result; } T sum(int l, int r) const { return sum(r) - sum(l); } private: int size_; std::vector data_; }; } // namespace nono #include namespace nono { namespace internal { constexpr bool is_prime(unsigned long long n) { for (unsigned long long i = 2; i * i <= n; i++) { if (n % i == 0) return false; } return true; } } // namespace internal template class Modint { public: static_assert(internal::is_prime(MOD)); constexpr Modint(unsigned long long value = 0): value_(value % MOD) {} constexpr Modint pow(long long exp) const { Modint result(1); Modint base(*this); while (exp > 0) { if (exp & 1) { result *= base; } base *= base; exp >>= 1; } return result; } constexpr Modint inv() const { return pow(MOD - 2); } void set(unsigned long long value) { if (value >= MOD) value %= MOD; value_ = value; } unsigned long long get() const { return value_; } friend constexpr bool operator==(const Modint lhs, const Modint rhs) { return lhs.value_ == rhs.value_; } constexpr Modint& operator+=(const Modint other) { this->value_ += other.value_; if (this->value_ >= MOD) this->value_ -= MOD; return *this; } constexpr Modint& operator-=(const Modint other) { this->value_ += MOD - other.value_; if (this->value_ >= MOD) this->value_ -= MOD; return *this; } constexpr Modint& operator*=(const Modint other) { this->value_ *= other.value_; if (this->value_ >= MOD) this->value_ %= MOD; return *this; } constexpr Modint& operator/=(const Modint other) { return *this *= other.inv(); } constexpr friend Modint operator+(const Modint lhs, const Modint rhs) { return Modint(lhs) += rhs; } constexpr friend Modint operator-(const Modint lhs, const Modint rhs) { return Modint(lhs) -= rhs; } constexpr friend Modint operator*(const Modint lhs, const Modint rhs) { return Modint(lhs) *= rhs; } constexpr friend Modint operator/(const Modint lhs, const Modint rhs) { return Modint(lhs) /= rhs; } friend std::istream& operator>>(std::istream& stream, Modint& mint) { unsigned long long value; stream >> value; mint.set(value); return stream; } friend std::ostream& operator<<(std::ostream& stream, Modint mint) { stream << mint.get(); return stream; } private: unsigned long long value_; }; using Modint998244353 = Modint<998244353>; using Modint1000000007 = Modint<1000000007>; } // namespace nono void solve() { using Mint = nono::Modint998244353; constexpr int N = 300005; std::array fact, fact_inv; fact.fill(1); fact_inv.fill(1); for (int i = 1; i < N; i++) fact[i] = fact[i - 1] * i; fact_inv[N - 1] = fact[N - 1].inv(); for (int i = N - 1; i > 0; i--) fact_inv[i - 1] = fact_inv[i] * i; auto binom = [&](int n, int k) { return fact.at(n) * fact_inv.at(k) * fact_inv.at(n - k); }; int n; std::cin >> n; std::vector p(n); for (int i = 0; i < n; i++) std::cin >> p[i]; for (int i = 0; i < n; i++) p[i]--; nono::FenwickTree fenwick(n); Mint ans = 0; for (int i = 0; i < n; i++) { int small_left = fenwick.sum(0, p[i]); int big_left = i - small_left; int small_right = p[i] - small_left; int big_right = (n - p[i] - 1) - big_left; Mint left = binom(small_left + big_right, small_left); Mint right = binom(small_right + big_left, small_right); ans += left * right; fenwick.add(p[i], 1); } std::cout << ans << '\n'; } int main() { std::cin.tie(0)->sync_with_stdio(0); std::cout << std::fixed << std::setprecision(16); int t = 1; while (t--) solve(); }