#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for(int i = 0; i < n; i++)
#define rep2(i, x, n) for(int i = x; i <= n; i++)
#define rep3(i, x, n) for(int i = x; i >= n; i--)
#define elif else if
#define sp(x) fixed << setprecision(x)
#define pb push_back
#define eb emplace_back
#define all(x) x.begin(), x.end()
#define sz(x) (int)x.size()
using ll = long long;
using pii = pair<int, int>;
using pil = pair<int, ll>;
using pli = pair<ll, int>;
using pll = pair<ll, ll>;
const int MOD = 1000000007;
//const int MOD = 998244353;
const int inf = (1<<30)-1;
const ll INF = (1LL<<60)-1;
const double pi = acos(-1.0);
const double EPS = 1e-10;
template<typename T> bool chmax(T &x, const T &y) {return (x < y)? (x = y, true) : false;};
template<typename T> bool chmin(T &x, const T &y) {return (x > y)? (x = y, true) : false;};

struct Graph{
    struct edge{
        int to, id;
        edge(int to, int id) : to(to), id(id) {}
    };

    vector<vector<edge>> es;
    vector<int> used;
    vector<int> keep;
    const int n;

    Graph(int n) : n(n){
        es.resize(n), used.resize(n);
    }

    void add_edge(int from, int to, int id, bool directed = false){
        es[from].eb(to, id);
        if(!directed) es[to].eb(from, id);
    }

    int trace(int now, int pre){
        if(used[now]) return 1;
        used[now]++;
        for(auto &e: es[now]){
            if(e.to == pre) continue;
            int k = trace(e.to, now);
            if(k == 2) return 2;
            if(k == 1) {keep.eb(e.id); return used[now];}
        }
        return 0;
    }

    vector<int> find_loop(){
        keep.clear(), trace(0, -1);
        return keep;
    }
};

int main(){
    int N;
    cin >> N;
    Graph G(N);
    rep(i, N){
        int u, v; cin >> u >> v; u--, v--;
        G.add_edge(u, v, i);
    }
    vector<int> loop = G.find_loop();
    cout << sz(loop) << endl;
    for(auto &e: loop) cout << e+1 << ' '; cout << endl;
}