#include using namespace std; #define ALL(x) begin(x),end(x) #define rep(i,n) for(int i=0;i<(n);i++) #define debug(v) cout<<#v<<":";for(auto x:v){cout<bool chmax(T &a,const T &b){if(abool chmin(T &a,const T &b){if(b ostream &operator<<(ostream &os,const vector&v){ for(int i=0;i<(int)v.size();i++) os< istream &operator>>(istream &is,vector&v){ for(T &x:v)is>>x; return is; } template struct ModInt{ long long x; ModInt():x(0){} ModInt(long long y):x(y>=0?y%Mod:(Mod-(-y)%Mod)%Mod){} ModInt &operator+=(const ModInt &p){ if((x+=p.x)>=Mod) x-=Mod; return *this; } ModInt &operator-=(const ModInt &p){ if((x+=Mod-p.x)>=Mod)x-=Mod; return *this; } ModInt &operator*=(const ModInt &p){ x=(int)(1ll*x*p.x%Mod); return *this; } ModInt &operator/=(const ModInt &p){ (*this)*=p.inverse(); return *this; } ModInt operator-()const{return ModInt(-x);} ModInt operator+(const ModInt &p)const{return ModInt(*this)+=p;} ModInt operator-(const ModInt &p)const{return ModInt(*this)-=p;} ModInt operator*(const ModInt &p)const{return ModInt(*this)*=p;} ModInt operator/(const ModInt &p)const{return ModInt(*this)/=p;} bool operator==(const ModInt &p)const{return x==p.x;} bool operator!=(const ModInt &p)const{return x!=p.x;} ModInt inverse()const{ int a=x,b=Mod,u=1,v=0,t; while(b>0){ t=a/b; swap(a-=t*b,b);swap(u-=t*v,v); } return ModInt(u); } ModInt pow(long long n)const{ ModInt ret(1),mul(x); while(n>0){ if(n&1) ret*=mul; mul*=mul;n>>=1; } return ret; } friend ostream &operator<<(ostream &os,const ModInt &p){return os<>(istream &is,ModInt &a){long long t;is>>t;a=ModInt(t);return (is);} static int get_mod(){return Mod;} }; using mint=ModInt<1000000007>; // graph template // ref : https://ei1333.github.io/library/graph/graph-template.cpp template struct Edge{ int from,to; T w; int idx; Edge()=default; Edge(int from,int to,T w=1,int idx=-1):from(from),to(to),w(w),idx(idx){} operator int() const{return to;} }; template struct Graph{ vector>> g; int V,E; Graph()=default; Graph(int n):g(n),V(n),E(0){} size_t size(){ return g.size(); } void resize(int k){ g.resize(k); } inline const vector> &operator[](int k)const{ return (g.at(k)); } inline vector> &operator[](int k){ return (g.at(k)); } void add_directed_edge(int from,int to,T cost=1){ g[from].emplace_back(from,to,cost,E++); } void add_edge(int from,int to,T cost=1){ g[from].emplace_back(from,to,cost,E); g[to].emplace_back(to,from,cost,E++); } void read(int m,int pad=-1,bool weighted=false,bool directed=false){ for(int i=0;i>u>>v; u+=pad,v+=pad; T w=T(1); if(weighted) cin>>w; if(directed) add_directed_edge(u,v,w); else add_edge(u,v,w); } } }; struct UnionFind{ private: vector par,siz; public: int con; UnionFind(int n):par(n),siz(n,1),con(n){ iota(begin(par),end(par),0); } int root(int x){ return (par[x]==x?x:(par[x]=root(par[x]))); } bool sameroot(int x,int y){ return root(x)==root(y); } bool unite(int x,int y){ x=root(x);y=root(y); if(x==y) return false; if(siz[x]>n>>m; vector par(n+m+1000,-1); vector sz(n+m+1000,1); function get_par=[&](int cur){ if(par[cur]==-1) return cur; return get_par(par[cur]); }; Graph g(n+m+1000); int dum=n; mint i2=mint(2).inverse(); rep(i,m){ int u,v;cin>>u>>v;u--,v--; int up=get_par(u),vp=get_par(v); if(up==vp) continue; if(sz[up]==sz[vp]){ par[up]=dum; par[vp]=dum; g.add_directed_edge(dum,up,i2); g.add_directed_edge(dum,vp,i2); sz[dum]=sz[up]+sz[vp]; dum++; } else{ if(sz[up] res(n); function dfs=[&](int cur,mint cul){ if(cur