#include using namespace std; #define rep(i,n) for(ll i=0;i=0;i--) #define perl(i,r,l) for(ll i=r-1;i>=l;i--) #define fi first #define se second #define pb push_back #define ins insert #define pqueue(x) priority_queue,greater> #define all(x) (x).begin(),(x).end() #define CST(x) cout<; using vvl=vector>; using pl=pair; using vpl=vector; using vvpl=vector; const ll MOD=1000000007; const ll MOD9=998244353; const int inf=1e9+10; const ll INF=4e18; //const ll dy[8]={-1,0,1,0,1,1,-1,-1}; //const ll dx[8]={0,-1,0,1,1,-1,1,-1}; template inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; } template inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; } const int mod = MOD9; const int max_n = 200005; struct mint { ll x; // typedef long long ll; mint(ll x=0):x((x%mod+mod)%mod){} mint operator-() const { return mint(-x);} mint& operator+=(const mint a) { if ((x += a.x) >= mod) x -= mod; return *this; } mint& operator-=(const mint a) { if ((x += mod-a.x) >= mod) x -= mod; return *this; } mint& operator*=(const mint a) { (x *= a.x) %= mod; return *this;} mint operator+(const mint a) const { return mint(*this) += a;} mint operator-(const mint a) const { return mint(*this) -= a;} mint operator*(const mint a) const { return mint(*this) *= a;} mint pow(ll t) const { if (!t) return 1; mint a = pow(t>>1); a *= a; if (t&1) a *= *this; return a; } bool operator==(const mint &p) const { return x == p.x; } bool operator!=(const mint &p) const { return x != p.x; } // for prime mod mint inv() const { return pow(mod-2);} mint& operator/=(const mint a) { return *this *= a.inv();} mint operator/(const mint a) const { return mint(*this) /= a;} }; istream& operator>>(istream& is, mint& a) { return is >> a.x;} ostream& operator<<(ostream& os, const mint& a) { return os << a.x;} struct combination { vector fact, ifact; combination(int n):fact(n+1),ifact(n+1) { assert(n < 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; } mint operator()(int n, int k) { if (k < 0 || k > n) return 0; return fact[n]*ifact[k]*ifact[n-k]; } }comb(max_n); struct UnionFind { vector par; UnionFind(int n) : par(n, -1) {} int root(int x) { if (par[x] < 0) return x; else return par[x] = root(par[x]); } bool same(int x, int y) { return root(x) == root(y); } bool merge(int x, int y) { x = root(x); y = root(y); if (x == y) return false; if (par[x] > par[y]) swap(x, y); par[x] += par[y]; par[y] = x; return true; } int size(int x) { return -par[root(x)]; } }; map memo[16]; ll n; mint calc(ll p,ll q){//pはパスの本数、qは残り頂点 辺が1本かつq==n-2の時場合わけ if(memo[p].count(q))return memo[p][q]; mint ret=0; for(int i=0;i<=q;i++){ ret+=comb(q,i)*comb(i+p-1,i)*comb.fact[i]; } ret*=comb.fact[p-1]; rep(i,p-1)ret*=2; if(q==n-2)ret-=1; memo[p][q]=ret; return ret; } int main(){ ll m;cin >> n >>m; vpl v(m);vl pls(2*m); rep(i,m){ cin >> v[i].fi >> v[i].se; pls[i*2]=v[i].fi; pls[i*2+1]=v[i].se; } sort(all(pls)); pls.erase(unique(all(pls)),pls.end()); rep(i,m){ v[i].fi=lower_bound(all(pls),v[i].fi)-pls.begin(); v[i].se=lower_bound(all(pls),v[i].se)-pls.begin(); } ll k=pls.size(); mint ans=0; for(int i=3;i<=n;i++)ans+=comb(n,i)*comb.fact[i-1]/2; repl(bit,1,1< deg(k); ll cycle=0; rep(i,m){ if(bit>>i&1){ ll a=v[i].fi,b=v[i].se; if(uf.same(a,b))cycle++; uf.merge(a,b); deg[a]++;deg[b]++; } } bool flag=true; mint ret=0; rep(i,k)if(deg[i]>=3)flag=false; if(cycle>=2)flag=false; if(!flag)continue; if(cycle==1){ sort(all(deg)); if(!binary_search(all(deg),1))ret=1; } else { ll cnt=0,rem=0; rep(i,k){ if(deg[i]==1)cnt++; if(deg[i]>=1)rem++; } cnt/=2;rem=n-rem; ret=calc(cnt,rem); } //cout << ret <