#define _USE_MATH_DEFINES #include using namespace std; #define FOR(i,m,n) for(int i=(m);i<(n);++i) #define REP(i,n) FOR(i,0,n) #define ALL(v) (v).begin(),(v).end() using ll = long long; const int INF = 0x3f3f3f3f; const ll LINF = 0x3f3f3f3f3f3f3f3fLL; const double EPS = 1e-8; const int MOD = 998244353; const int dy[] = {1, 0, -1, 0}, dx[] = {0, -1, 0, 1}; const int dy8[] = {1, 1, 0, -1, -1, -1, 0, 1}, dx8[] = {0, -1, -1, -1, 0, 1, 1, 1}; template inline bool chmax(T &a, U b) { return a < b ? (a = b, true) : false; } template inline bool chmin(T &a, U b) { return a > b ? (a = b, true) : false; } struct IOSetup { IOSetup() { cin.tie(nullptr); ios_base::sync_with_stdio(false); cout << fixed << setprecision(20); } } iosetup; int mod = MOD; struct ModInt { unsigned val; ModInt(): val(0) {} ModInt(ll x) : val(x >= 0 ? x % mod : x % mod + mod) {} ModInt pow(ll exponent) const { ModInt tmp = *this, res = 1; while (exponent > 0) { if (exponent & 1) res *= tmp; tmp *= tmp; exponent >>= 1; } return res; } ModInt &operator+=(const ModInt &x) { if((val += x.val) >= mod) val -= mod; return *this; } ModInt &operator-=(const ModInt &x) { if((val += mod - x.val) >= mod) val -= mod; return *this; } ModInt &operator*=(const ModInt &x) { val = static_cast(val) * x.val % mod; return *this; } ModInt &operator/=(const ModInt &x) { // assert(__gcd(static_cast(x.val), mod) == 1); unsigned a = x.val, b = mod; int u = 1, v = 0; while (b) { unsigned tmp = a / b; swap(a -= tmp * b, b); swap(u -= tmp * v, v); } return *this *= u; } bool operator==(const ModInt &x) const { return val == x.val; } bool operator!=(const ModInt &x) const { return val != x.val; } bool operator<(const ModInt &x) const { return val < x.val; } bool operator<=(const ModInt &x) const { return val <= x.val; } bool operator>(const ModInt &x) const { return val > x.val; } bool operator>=(const ModInt &x) const { return val >= x.val; } ModInt &operator++() { if (++val == mod) val = 0; return *this; } ModInt operator++(int) { ModInt res = *this; ++*this; return res; } ModInt &operator--() { val = (val == 0 ? mod : val) - 1; return *this; } ModInt operator--(int) { ModInt res = *this; --*this; return res; } ModInt operator+() const { return *this; } ModInt operator-() const { return ModInt(val ? mod - val : 0); } ModInt operator+(const ModInt &x) const { return ModInt(*this) += x; } ModInt operator-(const ModInt &x) const { return ModInt(*this) -= x; } ModInt operator*(const ModInt &x) const { return ModInt(*this) *= x; } ModInt operator/(const ModInt &x) const { return ModInt(*this) /= x; } friend ostream &operator<<(ostream &os, const ModInt &x) { return os << x.val; } friend istream &operator>>(istream &is, ModInt &x) { ll val; is >> val; x = ModInt(val); return is; } }; ModInt abs(const ModInt &x) { return x; } struct Combinatorics { int val; // "val!" and "mod" must be disjoint. vector fact, fact_inv, inv; Combinatorics(int val = 10000000) : val(val), fact(val + 1), fact_inv(val + 1), inv(val + 1) { fact[0] = 1; FOR(i, 1, val + 1) fact[i] = fact[i - 1] * i; fact_inv[val] = ModInt(1) / fact[val]; for (int i = val; i > 0; --i) fact_inv[i - 1] = fact_inv[i] * i; FOR(i, 1, val + 1) inv[i] = fact[i - 1] * fact_inv[i]; } ModInt nCk(int n, int k) const { if (n < 0 || n < k || k < 0) return ModInt(0); // assert(n <= val && k <= val); return fact[n] * fact_inv[k] * fact_inv[n - k]; } ModInt nPk(int n, int k) const { if (n < 0 || n < k || k < 0) return ModInt(0); // assert(n <= val); return fact[n] * fact_inv[n - k]; } ModInt nHk(int n, int k) const { if (n < 0 || k < 0) return ModInt(0); return k == 0 ? ModInt(1) : nCk(n + k - 1, k); } }; struct UnionFind { UnionFind(int n) : data(n, -1) {} int root(int ver) { return data[ver] < 0 ? ver : data[ver] = root(data[ver]); } bool unite(int u, int v) { u = root(u); v = root(v); if (u == v) return false; if (data[u] > data[v]) swap(u, v); data[u] += data[v]; data[v] = u; return true; } bool same(int u, int v) { return root(u) == root(v); } int size(int ver) { return -data[root(ver)]; } private: vector data; }; int main() { int n, m; cin >> n >> m; if (n < 3) { cout << 0 << '\n'; return 0; } Combinatorics com(n); map, ModInt> memo; function rec = [&](int block, int rem) { if (memo.count({block, rem}) == 1) return memo[{block, rem}]; ModInt tmp = 0; FOR(i, block, block + rem + 1) { // cout << block << ' ' << rem << ' ' << com.nCk(rem, i - block) * com.fact[i] << '\n'; tmp += com.nCk(rem, i - block) * com.fact[i]; } return memo[{block, rem}] = tmp; }; vector dp(n + 1, ModInt(0)); dp[3] = 1; FOR(i, 4, n + 1) dp[i] = dp[i - 1] * i - dp[i - 2] * (i - 1) + 1LL * (i - 1) * (i - 2) / 2; vector a(m), b(m), comp; REP(i, m) { cin >> a[i] >> b[i], --a[i], --b[i]; comp.emplace_back(a[i]); comp.emplace_back(b[i]); } sort(ALL(comp)); comp.erase(unique(ALL(comp)), comp.end()); int x = comp.size(); REP(i, m) { a[i] = lower_bound(ALL(comp), a[i]) - comp.begin(); b[i] = lower_bound(ALL(comp), b[i]) - comp.begin(); } ModInt ans = dp[n]; FOR(i, 1, 1 << m) { UnionFind uf(x); vector cnt(x, 0); REP(j, m) { if (i >> j & 1) { uf.unite(a[j], b[j]); ++cnt[a[j]]; ++cnt[b[j]]; } } int united = 0; bool ok = true, loop = true; REP(i, x) { ok &= cnt[i] <= 2; loop &= cnt[i] == 0 || cnt[i] == 2; if (uf.size(i) > 1 && uf.root(i) == i) ++united; } if (!ok) continue; if (loop) { if (united == 1) ans += __builtin_popcount(i) & 1 ? -1 : 1; continue; } map mp; REP(i, x) ++mp[uf.root(i)]; int block = 0, sum = 0, mx = 0; for (auto [key, cnt] : mp) { if (cnt >= 2) { ++block; sum += cnt; chmax(mx, cnt); } } ModInt tmp = rec(block - 1, n - sum); if (sum == 2) tmp -= 1; // cout << tmp * ModInt(2).pow(block - 1) << '\n'; ans += tmp * (__builtin_popcount(i) & 1 ? -1 : 1) * ModInt(2).pow(block - 1); } cout << ans << '\n'; return 0; }