#include #define REP_(i, a_, b_, a, b, ...) \ for (int i = (a), END_##i = (b); i < END_##i; ++i) #define REP(i, ...) REP_(i, __VA_ARGS__, __VA_ARGS__, 0, __VA_ARGS__) #define ALL(x) std::begin(x), std::end(x) using i64 = long long; #include using Mint = atcoder::modint998244353; std::ostream &operator<<(std::ostream &os, const Mint &m) { return os << m.val(); } template inline bool chmax(T &a, U b) { return a < b and ((a = std::move(b)), true); } template inline bool chmin(T &a, U b) { return a > b and ((a = std::move(b)), true); } template inline int ssize(const T &a) { return (int) a.size(); } template inline std::ostream &print_one(const T &x, char endc) { if constexpr (std::is_same_v) { return std::cout << (x ? "Yes" : "No") << endc; } else { return std::cout << x << endc; } } template inline std::ostream &print(const T &x) { return print_one(x, '\n'); } template std::ostream &print(const T &head, Ts... tail) { return print_one(head, ' '), print(tail...); } inline std::ostream &print() { return std::cout << '\n'; } template std::ostream &print_seq(const Container &a, std::string_view sep = " ", std::string_view ends = "\n", std::ostream &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::ostream &operator<<(std::ostream &os, const T &a) { return print_seq(a, ", ", "", (os << "{")) << "}"; } struct VersatileInput { template operator T() const { T x; std::cin >> x; return x; } struct Sized { std::size_t n; template operator T() const { T x(n); for (auto &e: x) std::cin >> e; return x; } }; Sized operator()(std::size_t n) const { return {n}; } } const in; inline void check(bool cond, const char *message = "!ERROR!") { if (not cond) throw std::runtime_error(message); } #ifdef MY_DEBUG #include "debug_dump.hpp" #else #define DUMP(...) #define cerr if(false)std::cerr #endif using namespace std; // Disjoint half-open intervals [l, r) (mapping l to r). class IntervalMap : public std::map { private: // If true, automatically merges [l, c) and [c, r). bool merge_adjacent; public: i64 length; IntervalMap(bool merge_adjacent = true) : merge_adjacent(merge_adjacent), length(0) {} // Returns the interval [l, r) which contains p if available. // Otherwise returns this->end(). std::map::iterator find_interval(i64 p) { auto it = upper_bound(p); if (it != begin()) { --it; if (it->second > p) return it; } return end(); } // Inserts interval [l, r) void add_interval(i64 l, i64 r) { auto itl = upper_bound(l), itr = lower_bound(r + merge_adjacent); if (itl != begin()) { --itl; if (itl->second <= l - merge_adjacent) ++itl; } if (itl != itr) { l = std::min(l, itl->first); r = std::max(r, std::prev(itr)->second); for (auto it = itl; it != itr;) { length -= it->second - it->first; it = erase(it); } //erase(itl, itr); } (*this)[l] = r; length += r - l; } // Are p and q in the same interval? bool same(i64 p, i64 q) { const auto it = find_interval(p); return it != end() and it->first <= q and q < it->second; } }; template struct Factorials { // factorials and inverse factorials. std::vector fact, ifact; // n: max cached value. Factorials(int n) : fact(n + 1), ifact(n + 1) { assert(n >= 0); assert(n < T::mod()); fact[0] = 1; for (int i = 1; i <= n; ++i) { fact[i] = fact[i - 1] * i; } ifact[n] = fact[n].inv(); for (int i = n; i >= 1; --i) { ifact[i - 1] = ifact[i] * i; } } // Combination (nCk) T C(int n, int k) const { if (k < 0 || k > n) return 0; return fact[n] * ifact[k] * ifact[n - k]; } }; auto solve() { int n = in; vector P = in(n); vector ix(n); REP(i, n) { ix[P[i]] = i; } Factorials fs(n + 1); IntervalMap imap(true); Mint ans = 1; REP(i, n) { int j = ix[i]; if (imap.find_interval(j) != imap.end()) continue; auto rit = imap.lower_bound(j); if (rit == imap.end() or rit == imap.begin()) { imap.add_interval(j, j + 1); } else { i64 r = prev(imap.end())->second; i64 l = imap.begin()->first; i64 s = (r - l) - imap.length; if (s > 1) { ans *= s; } imap.add_interval(j, j + 1); } // DUMP(i, imap, ans); // vector dbg(n, "_"); // for (auto[l, r]: imap) { // for (i64 j = l; j < r; ++j) { // dbg[j] = to_string(P[j]); // } // } // DUMP(i, dbg); } return ans; } int main() { ios_base::sync_with_stdio(false), cin.tie(nullptr); cout << std::fixed << std::setprecision(18); const int T = 1;//in; REP(t, T) { auto ans = solve(); print(ans); } }