#define LOCAL #include using namespace std; #pragma region Macros typedef long long ll; typedef __int128_t i128; typedef unsigned int uint; typedef unsigned long long ull; #define ALL(x) (x).begin(), (x).end() template istream& operator>>(istream& is, vector& v) { for (T& x : v) is >> x; return is; } template ostream& operator<<(ostream& os, const vector& v) { for (int i = 0; i < (int)v.size(); i++) { os << v[i] << (i + 1 == (int)v.size() ? "" : " "); } return os; } template ostream& operator<<(ostream& os, const pair& p) { os << '(' << p.first << ',' << p.second << ')'; return os; } template ostream& operator<<(ostream& os, const tuple& t) { os << '(' << get<0>(t) << ',' << get<1>(t) << ',' << get<2>(t) << ')'; return os; } template ostream& operator<<(ostream& os, const tuple& t) { os << '(' << get<0>(t) << ',' << get<1>(t) << ',' << get<2>(t) << ',' << get<3>(t) << ')'; return os; } template ostream& operator<<(ostream& os, const map& m) { os << '{'; for (auto itr = m.begin(); itr != m.end();) { os << '(' << itr->first << ',' << itr->second << ')'; if (++itr != m.end()) os << ','; } os << '}'; return os; } template ostream& operator<<(ostream& os, const unordered_map& m) { os << '{'; for (auto itr = m.begin(); itr != m.end();) { os << '(' << itr->first << ',' << itr->second << ')'; if (++itr != m.end()) os << ','; } os << '}'; return os; } template ostream& operator<<(ostream& os, const set& s) { os << '{'; for (auto itr = s.begin(); itr != s.end();) { os << *itr; if (++itr != s.end()) os << ','; } os << '}'; return os; } template ostream& operator<<(ostream& os, const multiset& s) { os << '{'; for (auto itr = s.begin(); itr != s.end();) { os << *itr; if (++itr != s.end()) os << ','; } os << '}'; return os; } template ostream& operator<<(ostream& os, const unordered_set& s) { os << '{'; for (auto itr = s.begin(); itr != s.end();) { os << *itr; if (++itr != s.end()) os << ','; } os << '}'; return os; } template ostream& operator<<(ostream& os, const deque& v) { for (int i = 0; i < (int)v.size(); i++) { os << v[i] << (i + 1 == (int)v.size() ? "" : " "); } return os; } void debug_out() { cerr << '\n'; } template void debug_out(Head&& head, Tail&&... tail) { cerr << head; if (sizeof...(Tail) > 0) cerr << ", "; debug_out(move(tail)...); } #ifdef LOCAL #define debug(...) \ cerr << " "; \ cerr << #__VA_ARGS__ << " :[" << __LINE__ << ":" << __FUNCTION__ << "]" << '\n'; \ cerr << " "; \ debug_out(__VA_ARGS__) #else #define debug(...) 42 #endif template T gcd(T x, T y) { return y != 0 ? gcd(y, x % y) : x; } template T lcm(T x, T y) { return x / gcd(x, y) * y; } template inline bool chmin(T1& a, T2 b) { if (a > b) { a = b; return true; } return false; } template inline bool chmax(T1& a, T2 b) { if (a < b) { a = b; return true; } return false; } #pragma endregion /** * @brief modint * @docs docs/modulo/modint.md */ template class modint { using i64 = int64_t; using u32 = uint32_t; using u64 = uint64_t; public: u32 v; constexpr modint(const i64 x = 0) noexcept : v(x < 0 ? mod - 1 - (-(x + 1) % mod) : x % mod) {} constexpr u32& value() noexcept { return v; } constexpr const u32& value() const noexcept { return v; } constexpr modint operator+(const modint& rhs) const noexcept { return modint(*this) += rhs; } constexpr modint operator-(const modint& rhs) const noexcept { return modint(*this) -= rhs; } constexpr modint operator*(const modint& rhs) const noexcept { return modint(*this) *= rhs; } constexpr modint operator/(const modint& rhs) const noexcept { return modint(*this) /= rhs; } constexpr modint& operator+=(const modint& rhs) noexcept { v += rhs.v; if (v >= mod) v -= mod; return *this; } constexpr modint& operator-=(const modint& rhs) noexcept { if (v < rhs.v) v += mod; v -= rhs.v; return *this; } constexpr modint& operator*=(const modint& rhs) noexcept { v = (u64)v * rhs.v % mod; return *this; } constexpr modint& operator/=(const modint& rhs) noexcept { return *this *= rhs.pow(mod - 2); } constexpr modint pow(u64 exp) const noexcept { modint self(*this), res(1); while (exp > 0) { if (exp & 1) res *= self; self *= self; exp >>= 1; } return res; } constexpr modint& operator++() noexcept { if (++v == mod) v = 0; return *this; } constexpr modint& operator--() noexcept { if (v == 0) v = mod; return --v, *this; } constexpr modint operator++(int) noexcept { modint t = *this; return ++*this, t; } constexpr modint operator--(int) noexcept { modint t = *this; return --*this, t; } constexpr modint operator-() const noexcept { return modint(mod - v); } template friend constexpr modint operator+(T x, modint y) noexcept { return modint(x) + y; } template friend constexpr modint operator-(T x, modint y) noexcept { return modint(x) - y; } template friend constexpr modint operator*(T x, modint y) noexcept { return modint(x) * y; } template friend constexpr modint operator/(T x, modint y) noexcept { return modint(x) / y; } constexpr bool operator==(const modint& rhs) const noexcept { return v == rhs.v; } constexpr bool operator!=(const modint& rhs) const noexcept { return v != rhs.v; } constexpr bool operator!() const noexcept { return !v; } friend istream& operator>>(istream& s, modint& rhs) noexcept { i64 v; rhs = modint{(s >> v, v)}; return s; } friend ostream& operator<<(ostream& s, const modint& rhs) noexcept { return s << rhs.v; } }; /** * @brief UnionFind * @docs docs/datastructure/UnionFind.md */ struct UnionFind { int num; vector par, rank; UnionFind(int n) : num(n), par(n), rank(n, 1) { iota(par.begin(), par.end(), 0); } int root(int x) { return (par[x] == x ? x : par[x] = root(par[x])); } bool merge(int x, int y) { x = root(x); y = root(y); if (x == y) return false; if (rank[x] < rank[y]) swap(x, y); par[y] = x; rank[x] += rank[y]; num--; return true; } bool same(int x, int y) { return root(x) == root(y); } int size(int x) { return rank[root(x)]; } int count() { return num; } int operator[](int x) { return root(x); } }; /** * @brief combination * @docs docs/combinatorics/combination.md */ template struct Combination { vector _fac, _inv, _finv; Combination(int n) : _fac(n + 1), _inv(n + 1), _finv(n + 1) { _fac[0] = _finv[n] = _inv[0] = 1; for (int i = 1; i <= n; i++) _fac[i] = _fac[i - 1] * i; _finv[n] /= _fac[n]; for (int i = n - 1; i >= 0; i--) _finv[i] = _finv[i + 1] * (i + 1); for (int i = 1; i <= n; i++) _inv[i] = _finv[i] * _fac[i - 1]; } M fac(int k) const { return _fac[k]; } M finv(int k) const { return _finv[k]; } M inv(int k) const { return _inv[k]; } M P(int n, int r) const { if (n < 0 || r < 0 || n < r) return 0; return _fac[n] * _finv[n - r]; } M C(int n, int r) const { if (n < 0 || r < 0 || n < r) return 0; return _fac[n] * _finv[r] * _finv[n - r]; } }; /** * @brief Number Theoretic Transform * @docs docs/convolution/NumberTheoreticTransform.md */ template struct NumberTheoreticTransform { using Mint = modint; vector roots; vector rev; int base, max_base; Mint root; NumberTheoreticTransform() : base(1), rev{0, 1}, roots{Mint(0), Mint(1)} { int tmp = mod - 1; for (max_base = 0; tmp % 2 == 0; max_base++) tmp >>= 1; root = 2; while (root.pow((mod - 1) >> 1) == 1) root++; root = root.pow((mod - 1) >> max_base); } void ensure_base(int nbase) { if (nbase <= base) return; rev.resize(1 << nbase); for (int i = 0; i < (1 << nbase); i++) { rev[i] = (rev[i >> 1] >> 1) | ((i & 1) << (nbase - 1)); } roots.resize(1 << nbase); for (; base < nbase; base++) { Mint z = root.pow(1 << (max_base - 1 - base)); for (int i = 1 << (base - 1); i < (1 << base); i++) { roots[i << 1] = roots[i]; roots[i << 1 | 1] = roots[i] * z; } } } void ntt(vector& a) { const int n = a.size(); int zeros = __builtin_ctz(n); ensure_base(zeros); int shift = base - zeros; for (int i = 0; i < n; i++) { if (i < (rev[i] >> shift)) { swap(a[i], a[rev[i] >> shift]); } } for (int k = 1; k < n; k <<= 1) { for (int i = 0; i < n; i += (k << 1)) { for (int j = 0; j < k; j++) { Mint z = a[i + j + k] * roots[j + k]; a[i + j + k] = a[i + j] - z; a[i + j] = a[i + j] + z; } } } } vector multiply(vector a, vector b) { int need = a.size() + b.size() - 1; int nbase = 1; while ((1 << nbase) < need) nbase++; ensure_base(nbase); int sz = 1 << nbase; a.resize(sz, Mint(0)); b.resize(sz, Mint(0)); ntt(a); ntt(b); Mint inv_sz = 1 / Mint(sz); for (int i = 0; i < sz; i++) a[i] *= b[i] * inv_sz; reverse(a.begin() + 1, a.end()); ntt(a); a.resize(need); return a; } vector multiply(vector a, vector b) { vector A(a.size()), B(b.size()); for (int i = 0; i < a.size(); i++) A[i] = Mint(a[i]); for (int i = 0; i < b.size(); i++) B[i] = Mint(b[i]); vector C = multiply(A, B); vector res(C.size()); for (int i = 0; i < C.size(); i++) res[i] = C[i].v; return res; } }; const int INF = 1e9; const long long IINF = 1e18; const int dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1}; const char dir[4] = {'D', 'R', 'U', 'L'}; // const long long MOD = 1000000007; const long long MOD = 998244353; using mint = modint; int main() { cin.tie(0); ios::sync_with_stdio(false); Combination COM(5010); int N, M; cin >> N >> M; vector P(N); cin >> P; vector> S(N + 1, vector(M + 1, 0)); for (int i = 1; i <= N; i++) { for (int j = 1; j <= M; j++) { if (j > i) continue; if (j == 1) S[i][j] = 1; else S[i][j] = S[i - 1][j - 1] + S[i - 1][j] * j; } } UnionFind UF(N); for (int i = 0; i < N; i++) UF.merge(i, --P[i]); vector v; vector check(N, false); for (int i = 0; i < N; i++) { if (check[UF[i]]) continue; check[UF[i]] = true; v.emplace_back(UF.size(i)); } int n = v.size(); vector> a(n); for (int i = 0; i < n; i++) { for (int j = 0; j < v[i]; j++) { if (j == v[i] - 1) a[i].emplace_back(1); else a[i].emplace_back(COM.C(v[i], j)); } } NumberTheoreticTransform NTT; auto dfs = [&](auto self, int l, int r) -> vector { if (r - l == 1) return a[l]; int mid = (l + r) >> 1; vector L = self(self, l, mid), R = self(self, mid, r); return NTT.multiply(L, R); }; vector dp = dfs(dfs, 0, n); mint ans = 0; for (int i = 0; i < dp.size(); i++) { mint add = dp[i] * S[N - i][M]; if (i & 1) ans -= add; else ans += add; } cout << ans << '\n'; }