#include #include using namespace std; using namespace atcoder; typedef long long int ll; typedef long double ld; typedef vector vi; typedef vector vvi; typedef vector vvvi; typedef vector vvvvi; typedef pair pi; typedef pair ppi; typedef pair pppi; typedef pair ppppi; #define FOR(i,l,r) for(ll i=l;i=l;i--) #define RREP(i,n) RFOR(i,0,n) #define ALL(x) x.begin(),x.end() #define F first #define S second #define BS(A,x) binary_search(ALL(A),x) #define LB(A,x) (ll)(lower_bound(ALL(A),x)-A.begin()) #define UB(A,x) (ll)(upper_bound(ALL(A),x)-A.begin()) #define COU(A,x) (UB(A,x)-LB(A,x)) #define sz(c) ((ll)(c).size()) /* #include namespace mp=boost::multiprecision; using Bint=mp::cpp_int; */ templateusing min_priority_queue=priority_queue,greater>; templateostream&operator<<(ostream&os,pair&p){os<istream&operator>>(istream&is,pair&p){is>>p.F>>p.S;return is;} templateostream&operator<<(ostream&os,vector&v){REP(i,sz(v))os<istream&operator>>(istream&is,vector&v){for(T&in:v)is>>in;return is;} templatebool chmax(T&a,T b){if(abool chmin(T&a,T b){if(b vm; typedef vector vvm; typedef vector vvvm; typedef vector vvvvm; ostream&operator<<(ostream&os,mint&a){os<>N>>M; mcf_graphG(N+2); vvi E(N),F(N); REP(i,M){ ll u,v;cin>>u>>v;u--;v--; E[u].emplace_back(v); F[v].emplace_back(u); G.add_edge(u,v,1,1); } REP(i,N){ G.add_edge(i,N+1,sz(F[i]),0); G.add_edge(N,i,sz(E[i]),0); } G.flow(N,N+1); auto es=G.edges(); vectorans; REP(i,M){ if(es[i].flow)ans.emplace_back(pi(es[i].from+1,es[i].to+1)); } cout<