#define NDEBUG #include #include #include #include #include #include #include #include template struct vec; template struct seq_view{ using Ref = typename std::iterator_traits::reference; using Elem = typename std::iterator_traits::value_type; Iter a, b; Iter begin() const { return a; } Iter end() const { return b; } int size() const { return (int)(b-a); } seq_view(Iter first, Iter last) : a(first), b(last) {} seq_view sort() const { std::sort(a, b); return *this; } Ref& operator[](int x){ return *(a+x); } template, class ret = vec> ret sorti(F f = F()) const { ret x(size()); for(int i=0; i> ret col() const { return ret(begin(), end()); } template, class ret = vec>> ret rle(F eq = F()) const { auto x = ret(); for(auto& a : (*this)){ if(x.size() == 0 || !eq(x[x.size()-1].first, a)) x.emp(a, 1); else x[x.size()-1].second++; } return x; } template seq_view sort(F f) const { std::sort(a, b, f); return *this; } Iter uni() const { return std::unique(a, b); } Iter lb(const Elem& x) const { return std::lower_bound(a, b, x); } Iter ub(const Elem& x) const { return std::upper_bound(a, b, x); } int lbi(const Elem& x) const { return lb(x) - a; } int ubi(const Elem& x) const { return ub(x) - a; } seq_view bound(const Elem& l, const Elem& r) const { return { lb(l), lb(r) }; } template Iter lb(const Elem& x, F f) const { return std::lower_bound(a, b, x, f); } template Iter ub(const Elem& x, F f) const { return std::upper_bound(a, b, x, f); } template Iter when_true_to_false(F f) const { if(a == b) return a; return std::lower_bound(a, b, *a, [&](const Elem& x, const Elem&){ return f(x); }); } seq_view same(Elem x) const { return { lb(x), ub(x) }; } template auto map(F f) const { vec r; for(auto& x : *this) r.emp(f(x)); return r; } Iter max() const { return std::max_element(a, b); } Iter min() const { return std::min_element(a, b); } template> Iter min(F f) const { return std::min_element(a, b, f); } seq_view rev() const { std::reverse(a, b); return *this; } }; template struct vec { using Base = typename std::vector; using Iter = typename Base::iterator; using CIter = typename Base::const_iterator; using View = seq_view; using CView = seq_view; vec(){} explicit vec(int n, const Elem& value = Elem()) : a(0 vec(I2 first, I2 last) : a(first, last) {} vec(std::initializer_list il) : a(std::move(il)) {} vec(Base b) : a(std::move(b)) {} operator Base() const { return a; } Iter begin(){ return a.begin(); } CIter begin() const { return a.begin(); } Iter end(){ return a.end(); } CIter end() const { return a.end(); } int size() const { return a.size(); } bool empty() const { return a.empty(); } Elem& back(){ return a.back(); } const Elem& back() const { return a.back(); } vec sortunied(){ vec x = *this; x().sort(); x.a.erase(x().uni(), x.end()); return x; } Iter operator()(int x){ return a.begin() + x; } CIter operator()(int x) const { return a.begin() + x; } View operator()(int l, int r){ return { (*this)(l), (*this)(r) }; } CView operator()(int l, int r) const { return { (*this)(l), (*this)(r) }; } View operator()(){ return (*this)(0,size()); } CView operator()() const { return (*this)(0,size()); } Elem& operator[](int x){ return a[x]; } const Elem& operator[](int x) const { return a[x]; } Base& operator*(){ return a; } const Base& operator*() const { return a; } vec& push(Elem args){ a.push_back(std::move(args)); return *this; } template vec& emp(Args &&... args){ a.emplace_back(std::forward(args) ...); return *this; } template vec& app(Range& x){ for(auto& v : a) emp(v); } Elem pop(){ Elem x = std::move(a.back()); a.pop_back(); return x; } bool operator==(const vec& r) const { return a == r.a; } bool operator!=(const vec& r) const { return a != r.a; } bool operator<(const vec& r) const { return a < r.a; } bool operator<=(const vec& r) const { return a <= r.a; } bool operator>(const vec& r) const { return a > r.a; } bool operator>=(const vec& r) const { return a >= r.a; } vec> pile(int n) const { return vec>(n, *this); } template vec& filter(F f){ int p = 0; for(int q=0; q IStr& operator>>(IStr& is, vec>& v){ for(auto& x:v){ is >> x.first >> x.second; } return is; } template IStr& operator>>(IStr& is, vec& v){ for(auto& x:v){ is >> x; } return is; } template OStr& operator<<(OStr& os, const vec& v){ for(int i=0; i namespace nachia{ template class CsrArray{ public: struct ListRange{ using iterator = typename std::vector::iterator; iterator begi, endi; iterator begin() const { return begi; } iterator end() const { return endi; } int size() const { return (int)std::distance(begi, endi); } Elem& operator[](int i) const { return begi[i]; } }; struct ConstListRange{ using iterator = typename std::vector::const_iterator; iterator begi, endi; iterator begin() const { return begi; } iterator end() const { return endi; } int size() const { return (int)std::distance(begi, endi); } const Elem& operator[](int i) const { return begi[i]; } }; private: int m_n; std::vector m_list; std::vector m_pos; public: CsrArray() : m_n(0), m_list(), m_pos() {} static CsrArray Construct(int n, std::vector> items){ CsrArray res; res.m_n = n; std::vector buf(n+1, 0); for(auto& [u,v] : items){ ++buf[u]; } for(int i=1; i<=n; i++) buf[i] += buf[i-1]; res.m_list.resize(buf[n]); for(int i=(int)items.size()-1; i>=0; i--){ res.m_list[--buf[items[i].first]] = std::move(items[i].second); } res.m_pos = std::move(buf); return res; } static CsrArray FromRaw(std::vector list, std::vector pos){ CsrArray res; res.m_n = pos.size() - 1; res.m_list = std::move(list); res.m_pos = std::move(pos); return res; } ListRange operator[](int u) { return ListRange{ m_list.begin() + m_pos[u], m_list.begin() + m_pos[u+1] }; } ConstListRange operator[](int u) const { return ConstListRange{ m_list.begin() + m_pos[u], m_list.begin() + m_pos[u+1] }; } int size() const { return m_n; } int fullSize() const { return (int)m_list.size(); } }; } // namespace nachia namespace nachia{ struct Graph { public: struct Edge{ int from, to; void reverse(){ std::swap(from, to); } }; Graph(int n = 0, bool undirected = false, int m = 0) : m_n(n), m_e(m), m_isUndir(undirected) {} Graph(int n, const std::vector>& edges, bool undirected = false) : m_n(n), m_isUndir(undirected){ m_e.resize(edges.size()); for(std::size_t i=0; i static Graph Input(Cin& cin, int n, bool undirected, int m, bool offset = 0){ Graph res(n, undirected, m); for(int i=0; i> u >> v; res[i].from = u - offset; res[i].to = v - offset; } return res; } int numVertices() const noexcept { return m_n; } int numEdges() const noexcept { return int(m_e.size()); } int addNode() noexcept { return m_n++; } int addEdge(int from, int to){ m_e.push_back({ from, to }); return numEdges() - 1; } Edge& operator[](int ei) noexcept { return m_e[ei]; } const Edge& operator[](int ei) const noexcept { return m_e[ei]; } Edge& at(int ei) { return m_e.at(ei); } const Edge& at(int ei) const { return m_e.at(ei); } auto begin(){ return m_e.begin(); } auto end(){ return m_e.end(); } auto begin() const { return m_e.begin(); } auto end() const { return m_e.end(); } bool isUndirected() const noexcept { return m_isUndir; } void reverseEdges() noexcept { for(auto& e : m_e) e.reverse(); } void contract(int newV, const std::vector& mapping){ assert(numVertices() == int(mapping.size())); for(int i=0; i induce(int num, const std::vector& mapping) const { int n = numVertices(); assert(n == int(mapping.size())); for(int i=0; i indexV(n), newV(num); for(int i=0; i= 0) indexV[i] = newV[mapping[i]]++; std::vector res; res.reserve(num); for(int i=0; i= 0) res[mapping[e.to]].addEdge(indexV[e.from], indexV[e.to]); return res; } CsrArray getEdgeIndexArray(bool undirected) const { std::vector> src; src.reserve(numEdges() * (undirected ? 2 : 1)); for(int i=0; i::Construct(numVertices(), src); } CsrArray getEdgeIndexArray() const { return getEdgeIndexArray(isUndirected()); } CsrArray getAdjacencyArray(bool undirected) const { std::vector> src; src.reserve(numEdges() * (undirected ? 2 : 1)); for(auto e : m_e){ src.emplace_back(e.from, e.to); if(undirected) src.emplace_back(e.to, e.from); } return CsrArray::Construct(numVertices(), src); } CsrArray getAdjacencyArray() const { return getAdjacencyArray(isUndirected()); } private: int m_n; std::vector m_e; bool m_isUndir; }; } // namespace nachia namespace nachia { struct Dsu{ private: int N; std::vector P; std::vector H; public: Dsu() : N(0) {} Dsu(int n) : N(n), P(n, -1), H(n) { for(int i=0; i= 0){ P[u] = P[v]; u = v; v = P[v]; } return P[u]; } int append(){ int n = P.size(); P.push_back(-1); H.push_back(n); return n; } int label(int u){ return H[leader(u)]; } int operator[](int u){ return H[leader(u)]; } void merge(int u, int v, int newLabel){ if(newLabel < 0) newLabel = u; u = leader(u); v = leader(v); if(u == v){ H[u] = newLabel; return; } N--; if(-P[u] < -P[v]) std::swap(u, v); P[u] += P[v]; H[P[v] = u] = newLabel; } int merge(int u, int v){ merge(u, v, u); return u; } int count(){ return N; } int size(int u){ return -P[leader(u)]; } bool same(int u, int v){ return leader(u) == leader(v); } }; } // namespace nachia namespace nachia{ struct HeavyLightDecomposition{ private: int N; std::vector P; std::vector PP; std::vector PD; std::vector D; std::vector I; std::vector rangeL; std::vector rangeR; public: HeavyLightDecomposition(const CsrArray& E = CsrArray::Construct(1, {}), int root = 0){ N = E.size(); P.assign(N, -1); I = {root}; I.reserve(N); for(int i=0; i<(int)I.size(); i++){ int p = I[i]; for(int e : E[p]) if(P[p] != e){ I.push_back(e); P[e] = p; } } std::vector Z(N, 1); std::vector nx(N, -1); PP.resize(N); for(int i=0; i=1; i--){ int p = I[i]; Z[P[p]] += Z[p]; if(nx[P[p]] == -1) nx[P[p]] = p; if(Z[nx[P[p]]] < Z[p]) nx[P[p]] = p; } for(int p : I) if(nx[p] != -1) PP[nx[p]] = p; PD.assign(N,N); PD[root] = 0; D.assign(N,0); for(int p : I) if(p != root){ PP[p] = PP[PP[p]]; PD[p] = std::min(PD[PP[p]], PD[P[p]]+1); D[p] = D[P[p]]+1; } rangeL.assign(N,0); rangeR.assign(N,0); for(int p : I){ rangeR[p] = rangeL[p] + Z[p]; int ir = rangeR[p]; for(int e : E[p]) if(P[p] != e) if(e != nx[p]){ rangeL[e] = (ir -= Z[e]); } if(nx[p] != -1){ rangeL[nx[p]] = rangeL[p] + 1; } } I.resize(N); for(int i=0; i PD[v]) u = P[PP[u]]; while(PP[u] != PP[v]){ u = P[PP[u]]; v = P[PP[v]]; } return (D[u] > D[v]) ? v : u; } int dist(int u, int v) const { return depth(u) + depth(v) - depth(lca(u,v)) * 2; } struct Range{ int l; int r; int size() const { return r-l; } bool includes(int x) const { return l <= x && x < r; } }; std::vector path(int r, int c, bool include_root = true, bool reverse_path = false) const { if(PD[c] < PD[r]) return {}; std::vector res(PD[c]-PD[r]+1); for(int i=0; i<(int)res.size()-1; i++){ res[i] = { rangeL[PP[c]], rangeL[c]+1 }; c = P[PP[c]]; } if(PP[r] != PP[c] || D[r] > D[c]) return {}; res.back() = { rangeL[r]+(include_root?0:1), rangeL[c]+1 }; if(res.back().l == res.back().r) res.pop_back(); if(!reverse_path) std::reverse(res.begin(),res.end()); else for(auto& a : res) a = { N - a.r, N - a.l }; return res; } Range subtree(int p){ return { rangeL[p], rangeR[p] }; } int median(int x, int y, int z) const { return lca(x,y) ^ lca(y,z) ^ lca(x,z); } int la(int from, int to, int d) const { if(d < 0) return -1; int g = lca(from,to); int dist0 = D[from] - D[g] * 2 + D[to]; if(dist0 < d) return -1; int p = from; if(D[from] - D[g] < d){ p = to; d = dist0 - d; } while(D[p] - D[PP[p]] < d){ d -= D[p] - D[PP[p]] + 1; p = P[PP[p]]; } return I[rangeL[p] - d]; } }; } // namespace nachia #include #include #include namespace nachia{ struct CInStream{ private: static const unsigned int INPUT_BUF_SIZE = 1 << 17; unsigned int p = INPUT_BUF_SIZE; static char Q[INPUT_BUF_SIZE]; public: using MyType = CInStream; char seekChar(){ if(p == INPUT_BUF_SIZE){ size_t len = fread(Q, 1, INPUT_BUF_SIZE, stdin); if(len != INPUT_BUF_SIZE) Q[len] = '\0'; p = 0; } return Q[p]; } void skipSpace(){ while(isspace(seekChar())) p++; } private: template T nextUInt(){ if constexpr (sp) skipSpace(); T buf = 0; while(true){ char tmp = seekChar(); if('9' < tmp || tmp < '0') break; buf = buf * 10 + (tmp - '0'); p++; } return buf; } public: uint32_t nextU32(){ return nextUInt(); } int32_t nextI32(){ skipSpace(); if(seekChar() == '-'){ p++; return (int32_t)(-nextUInt()); } return (int32_t)nextUInt(); } uint64_t nextU64(){ return nextUInt();} int64_t nextI64(){ skipSpace(); if(seekChar() == '-'){ p++; return (int64_t)(-nextUInt()); } return (int64_t)nextUInt(); } template T nextInt(){ skipSpace(); if(seekChar() == '-'){ p++; return - nextUInt(); } return nextUInt(); } char nextChar(){ skipSpace(); char buf = seekChar(); p++; return buf; } std::string nextToken(){ skipSpace(); std::string buf; while(true){ char ch = seekChar(); if(isspace(ch) || ch == '\0') break; buf.push_back(ch); p++; } return buf; } MyType& operator>>(unsigned int& dest){ dest = nextU32(); return *this; } MyType& operator>>(int& dest){ dest = nextI32(); return *this; } MyType& operator>>(unsigned long& dest){ dest = nextU64(); return *this; } MyType& operator>>(long& dest){ dest = nextI64(); return *this; } MyType& operator>>(unsigned long long& dest){ dest = nextU64(); return *this; } MyType& operator>>(long long& dest){ dest = nextI64(); return *this; } MyType& operator>>(std::string& dest){ dest = nextToken(); return *this; } MyType& operator>>(char& dest){ dest = nextChar(); return *this; } } cin; struct FastOutputTable{ char LZ[1000][4] = {}; char NLZ[1000][4] = {}; constexpr FastOutputTable(){ using u32 = uint_fast32_t; for(u32 d=0; d<1000; d++){ LZ[d][0] = ('0' + d / 100 % 10); LZ[d][1] = ('0' + d / 10 % 10); LZ[d][2] = ('0' + d / 1 % 10); LZ[d][3] = '\0'; } for(u32 d=0; d<1000; d++){ u32 i = 0; if(d >= 100) NLZ[d][i++] = ('0' + d / 100 % 10); if(d >= 10) NLZ[d][i++] = ('0' + d / 10 % 10); if(d >= 1) NLZ[d][i++] = ('0' + d / 1 % 10); NLZ[d][i++] = '\0'; } } }; struct COutStream{ private: using u32 = uint32_t; using u64 = uint64_t; using MyType = COutStream; static const u32 OUTPUT_BUF_SIZE = 1 << 17; static char Q[OUTPUT_BUF_SIZE]; static constexpr FastOutputTable TB = FastOutputTable(); u32 p = 0; static constexpr u32 P10(u32 d){ return d ? P10(d-1)*10 : 1; } static constexpr u64 P10L(u32 d){ return d ? P10L(d-1)*10 : 1; } template static void Fil(T& m, U& l, U x){ m = l/x; l -= m*x; } void next_dig9(u32 x){ u32 y; Fil(y, x, P10(6)); nextCstr(TB.LZ[y]); Fil(y, x, P10(3)); nextCstr(TB.LZ[y]); nextCstr(TB.LZ[x]); } public: void nextChar(char c){ Q[p++] = c; if(p == OUTPUT_BUF_SIZE){ fwrite(Q, p, 1, stdout); p = 0; } } void nextEoln(){ nextChar('\n'); } void nextCstr(const char* s){ while(*s) nextChar(*(s++)); } void nextU32(uint32_t x){ u32 y = 0; if(x >= P10(9)){ Fil(y, x, P10(9)); nextCstr(TB.NLZ[y]); next_dig9(x); } else if(x >= P10(6)){ Fil(y, x, P10(6)); nextCstr(TB.NLZ[y]); Fil(y, x, P10(3)); nextCstr(TB.LZ[y]); nextCstr(TB.LZ[x]); } else if(x >= P10(3)){ Fil(y, x, P10(3)); nextCstr(TB.NLZ[y]); nextCstr(TB.LZ[x]); } else if(x >= 1) nextCstr(TB.NLZ[x]); else nextChar('0'); } void nextI32(int32_t x){ if(x >= 0) nextU32(x); else{ nextChar('-'); nextU32((u32)-x); } } void nextU64(uint64_t x){ u32 y = 0; if(x >= P10L(18)){ Fil(y, x, P10L(18)); nextU32(y); Fil(y, x, P10L(9)); next_dig9(y); next_dig9(x); } else if(x >= P10L(9)){ Fil(y, x, P10L(9)); nextU32(y); next_dig9(x); } else nextU32(x); } void nextI64(int64_t x){ if(x >= 0) nextU64(x); else{ nextChar('-'); nextU64((u64)-x); } } template void nextInt(T x){ if(x < 0){ nextChar('-'); x = -x; } if(!(0 < x)){ nextChar('0'); return; } std::string buf; while(0 < x){ buf.push_back('0' + (int)(x % 10)); x /= 10; } for(int i=(int)buf.size()-1; i>=0; i--){ nextChar(buf[i]); } } void writeToFile(bool flush = false){ fwrite(Q, p, 1, stdout); if(flush) fflush(stdout); p = 0; } COutStream(){ Q[0] = 0; } ~COutStream(){ writeToFile(); } MyType& operator<<(unsigned int tg){ nextU32(tg); return *this; } MyType& operator<<(unsigned long tg){ nextU64(tg); return *this; } MyType& operator<<(unsigned long long tg){ nextU64(tg); return *this; } MyType& operator<<(int tg){ nextI32(tg); return *this; } MyType& operator<<(long tg){ nextI64(tg); return *this; } MyType& operator<<(long long tg){ nextI64(tg); return *this; } MyType& operator<<(const std::string& tg){ nextCstr(tg.c_str()); return *this; } MyType& operator<<(const char* tg){ nextCstr(tg); return *this; } MyType& operator<<(char tg){ nextChar(tg); return *this; } } cout; char CInStream::Q[INPUT_BUF_SIZE]; char COutStream::Q[OUTPUT_BUF_SIZE]; } // namespace nachia #define rep(i,n) for(int i=0; i<(int)(n); i++) int main(){ using namespace std; using Modint = atcoder::static_modint<998244353>; using nachia::cin; using nachia::cout; int N, M; cin >> N >> M; auto graph = nachia::Graph::Input(cin, N, false, M, 1); auto mtree = nachia::Graph(N, false); auto dsu = nachia::Dsu(N); graph.reverseEdges(); auto adj = graph.getAdjacencyArray(); rep(u,N) for(int v : adj[u]) if(!dsu.same(u, v)){ mtree.addEdge(u, dsu[v]); dsu.merge(u, v, u); } auto hld = nachia::HeavyLightDecomposition(mtree, N-1); auto ds = atcoder::fenwick_tree(N+1); auto rangeAdd = [&](int l, int r, Modint val){ ds.add(l, val); ds.add(r, -val); }; auto pointGet = [&](int p) -> Modint { return ds.sum(0, p+1); }; Modint ans = 0; rep(v,N){ sort(adj[v].begin(), adj[v].end(), [&](int a, int b){ return hld.toSeq(a) < hld.toSeq(b); }); Modint f = 1; for(int u : adj[v]) f += pointGet(hld.toSeq(u)); rep(i,adj[v].size()-1) f -= pointGet(hld.toSeq(hld.lca(adj[v][i], adj[v][i+1]))); auto [l,r] = hld.subtree(v); rangeAdd(l, r, f); ans += f; } cout << ans.val() << '\n'; return 0; }