#include <iostream> #include <algorithm> #include <string> #include <vector> #include <cmath> #include <map> #include <queue> #include <iomanip> #include <set> #include <tuple> #define mkp make_pair #define mkt make_tuple #define rep(i,n) for(int i = 0; i < (n); ++i) #define all(v) v.begin(),v.end() using namespace std; typedef long long ll; const ll MOD=1e9+7; template<class T> void chmin(T &a,const T &b){if(a>b) a=b;} template<class T> void chmax(T &a,const T &b){if(a<b) a=b;} struct Edge{ int from,to; ll cost; int id; Edge(){} Edge(int from,int to,ll cost=1,int id=0):from(from),to(to),cost(cost),id(id){} }; struct LowLink{ int N; vector<vector<Edge>> g; vector<int> ord,low,vis; vector<int> articulations; vector<Edge> bridges; LowLink(int N,vector<vector<Edge>> &g):N(N),g(g),ord(N),low(N),vis(N){} void dfs(int now,int par,int &cnt){ ord[now]=cnt++; vis[now]=1; bool isArt=false; int num=0; low[now]=ord[now]; for(auto e:g[now]){ if(e.to==par) continue; if(vis[e.to]){ chmin(low[now],ord[e.to]); }else{ num++; dfs(e.to,now,cnt); chmin(low[now],low[e.to]); if(ord[now]<low[e.to]) bridges.emplace_back(e); if(ord[now]<=low[e.to]) isArt=true; } } if(par==-1&&num>1) articulations.push_back(now); if(par!=-1&&isArt) articulations.push_back(now); } void build(){ int cnt=0; for(int i=0;i<N;i++) if(vis[i]==0) dfs(i,-1,cnt); } }; int main(){ cin.tie(0); ios::sync_with_stdio(false); int N; cin>>N; vector<vector<Edge>> g(N); rep(i,N){ int a,b; cin>>a>>b; a--;b--; g[a].emplace_back(Edge{a,b,1,i}); g[b].emplace_back(Edge{b,a,1,i}); } LowLink LL(N,g); LL.build(); vector<Edge> bridges=LL.bridges; vector<int> used(N,0); for(auto e:bridges) used[e.id]=1; vector<int> ans; rep(i,N) if(used[i]==0) ans.push_back(i); cout<<ans.size()<<endl; rep(i,ans.size()) cout<<ans[i]+1<<" "; cout<<endl; return 0; }