#include #define rep(i,n) for(int i=0;i<(n);i++) using namespace std; class union_find{ int n; vector p; public: union_find(int n):n(n),p(n,-1){} int find(int u){ return p[u]<0?u:p[u]=find(p[u]); } void unite(int u,int v){ u=find(u); v=find(v); if(u!=v){ if(p[v]>1)&0x55555555)+(x&0x55555555); x=((x>>2)&0x33333333)+(x&0x33333333); x=((x>>4)+x)&0x0f0f0f0f; x+=(x>>8); x+=(x>>16); return x&0x3f; } class mint{ static const int MOD=998244353; int x; public: mint():x(0){} mint(long long y){ x=y%MOD; if(x<0) x+=MOD; } mint& operator+=(const mint& m){ x+=m.x; if(x>=MOD) x-=MOD; return *this; } mint& operator-=(const mint& m){ x-=m.x; if(x< 0) x+=MOD; return *this; } mint& operator*=(const mint& m){ x=1LL*x*m.x%MOD; return *this; } mint& operator/=(const mint& m){ return *this*=inverse(m); } mint operator+(const mint& m)const{ return mint(*this)+=m; } mint operator-(const mint& m)const{ return mint(*this)-=m; } mint operator*(const mint& m)const{ return mint(*this)*=m; } mint operator/(const mint& m)const{ return mint(*this)/=m; } mint operator-()const{ return mint(-x); } friend mint inverse(const mint& m){ int a=m.x,b=MOD,u=1,v=0; while(b>0){ int t=a/b; a-=t*b; swap(a,b); u-=t*v; swap(u,v); } return u; } friend istream& operator>>(istream& is,mint& m){ long long t; is>>t; m=mint(t); return is; } friend ostream& operator<<(ostream& os,const mint& m){ return os<0;k>>=1,m*=m) if(k&1) res*=m; return res; } mint fact(int n){ static vector memo={1}; if(memo.size()<=n){ int k=memo.size(); memo.resize(n+1); for(;k<=n;k++) memo[k]=memo[k-1]*k; } return memo[n]; } mint fact_inverse(int n){ static vector memo={1}; if(memo.size()<=n){ int k=memo.size(); memo.resize(n+1); memo[n]=inverse(fact(n)); for(int i=n;i>k;i--) memo[i-1]=memo[i]*i; } return memo[n]; } mint choose(int n,int k,int type=0){ if(k==0) return 1; if(n< k) return 0; if(type==0){ return fact(n)*fact_inverse(k)*fact_inverse(n-k); } else{ if(k>n-k) k=n-k; mint res=fact_inverse(k); rep(i,k) res*=n-i; return res; } } mint g(int zero,int one){ static map,mint> memo; if(memo.count({zero,one})>0) return memo[{zero,one}]; mint res=0; rep(i,zero+1){ res+=choose(zero,i)*fact(i+one/2-1)*pow(mint(2),one/2-1); } return memo[{zero,one}]=res; } int n,m; vector> E; mint f(int S){ // S に含まれるすべての辺を含む K_n のサイクルの個数を求める map h; rep(i,m) if(S>>i&1) { auto [u,v]=E[i]; if(h.count(u)==0) h[u]=h.size(); if(h.count(v)==0) h[v]=h.size(); } int N=h.size(),loop_cnt=0; vector deg(N); union_find U(N); rep(i,m) if(S>>i&1) { auto [u,v]=E[i]; u=h[u]; v=h[v]; deg[u]++; deg[v]++; if(U.is_same(u,v)) loop_cnt++; U.unite(u,v); } int zero=count(deg.begin(),deg.end(),0)+n-N; int one =count(deg.begin(),deg.end(),1); rep(u,N) if(deg[u]>=3) return 0; if(loop_cnt>=2) return 0; if(loop_cnt==1) return one==0?1:0; mint res; if(zero==n){ res=0; for(int l=3;l<=n;l++){ res+=choose(n,l)*fact(l-1); } res/=2; } else{ res=g(zero,one); if(popcount(S)==1) res-=1; } return res; } int main(){ scanf("%d%d",&n,&m); E.resize(m); rep(i,m) scanf("%d%d",&E[i].first,&E[i].second), E[i].first--, E[i].second--; mint ans=0; rep(S,1<