#include"bits/stdc++.h"
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<<x<<' ';}cout<<endl;
#define mod 1000000007
using ll=long long;
const int INF=1000000000;
const ll LINF=1001002003004005006ll;
int dx[]={1,0,-1,0},dy[]={0,1,0,-1};
// ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}
template<class T>bool chmax(T &a,const T &b){if(a<b){a=b;return true;}return false;}
template<class T>bool chmin(T &a,const T &b){if(b<a){a=b;return true;}return false;}

struct IOSetup{
    IOSetup(){
        cin.tie(0);
        ios::sync_with_stdio(0);
        cout<<fixed<<setprecision(12);
    }
} iosetup;
 
template<typename T>
ostream &operator<<(ostream &os,const vector<T>&v){
    for(int i=0;i<(int)v.size();i++) os<<v[i]<<(i+1==(int)v.size()?"":" ");
    return os;
}
template<typename T>
istream &operator>>(istream &is,vector<T>&v){
    for(T &x:v)is>>x;
    return is;
}

// graph template
// ref : https://ei1333.github.io/library/graph/graph-template.cpp
template<typename T=int>
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<typename T=int>
struct Graph{
    vector<vector<Edge<T>>> g;
    int V,E;
    Graph()=default;
    Graph(int n):g(n),V(n),E(0){}

    int size(){
        return (int)g.size();
    }
    void resize(int k){
        g.resize(k);
        V=k;
    }
    inline const vector<Edge<T>> &operator[](int k)const{
        return (g.at(k));
    }
    inline vector<Edge<T>> &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<m;i++){
            int u,v;cin>>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);
        }
    }
};


/*
Namori Graph

loop_vertex[i] - loop_edge[i] loop_vertex[i+1]
forest : loop_vertexからぶら下がる木
         loop_vertexをroot, 0としてidふり直し
*/
template<typename T>
struct Namori{
    Graph<T> G;
    vector<int> loop_vertex;
    vector<Edge<T>> loop_edge;
    vector<Graph<int>> forest;

    Namori(Graph<T> G):G(G){
        int N=G.size();

        // loop 取り出し
        vector<bool> used(N, false);
        {
            vector<int> deg(N);
            queue<int> que;
            for(int i=0;i<N;i++){
                deg[i]=G[i].size();
                if(deg[i]==1){
                    que.push(i);
                    used[i]=true;
                }
            }

            while(not que.empty()){
                int cur=que.front();que.pop();

                for(auto &e:G[cur])if(not used[e]){
                    deg[e]--;
                    if(deg[e]==1){
                        que.push(e);
                        used[e]=true;
                    }
                }
            }
        }

        // loop順序
        {
            queue<int> que;
            vector<bool> visited(N, false);
            for(int i=0;i<N;i++){
                if(not used[i]){
                    que.push(i);
                    visited[i]=true;
                    loop_vertex.push_back(i);
                    break;
                }
            }
            while(not que.empty()){
                int cur=que.front();que.pop();
                for(auto &e:G[cur])if((not used[e]) and (not visited[e])){
                    visited[e]=true;
                    que.push(e);
                    loop_vertex.push_back(e);
                    loop_edge.emplace_back(e.from, e.to, e.w, e.idx);
                    break;
                }
            }
            for(auto &e:G[loop_vertex.back()])
                if(minmax(e.from, e.to)==minmax(loop_vertex[0], loop_vertex.back()))
                    loop_edge.push_back(e);
        }
        


        // forest 構築
        {
            vector<int> id(N, -1);
            for(int root:loop_vertex){
                vector<Edge<T>> es;
                int V=0;
                function<void(int,int)> dfs=[&](int par, int cur){
                    for(auto &e:G[cur])if(par!=e and (used[e])){
                        if(id[e]==-1) id[e]=V++;
                        es.emplace_back(id[cur], id[e], e.w, e.idx);
                        dfs(cur, e);
                    }
                };
                id[root]=V++;
                dfs(-1, root);

                Graph<T> g(V);
                for(auto &e:es) g.add_edge(e.from, e.to, e.w);
                forest.push_back(g);
            }
        }
    }
};

signed main(){
    int N;cin>>N;
    Graph<int> G(N);
    rep(i, N){
        int u,v;cin>>u>>v;u--,v--;
        G.add_edge(u, v);
    }

    Namori<int> namori(G);
    // debug(namori.loop_vertex);
    cout<<namori.loop_edge.size()<<"\n";
    rep(i, namori.loop_edge.size()) cout<<namori.loop_edge[i].idx+1<<(i+1==namori.loop_edge.size()?"\n":" ");
    return 0;
}