#include <iostream>
#include <vector>
#include <cmath>
#include <map>
#include <set>
#include <iomanip>
#include <queue>
#include <algorithm>
#include <numeric>
#include <deque>
#include <complex>
#include <cassert>

using namespace std;

vector<bool> cycle, visit;
set<int> st;

void dfs(vector<vector<pair<int, int>>> &E, int from){
    visit[from] = 1;
    for(auto [to, idx] : E[from]){
        if (!cycle[to]) continue;
        st.insert(idx);
        if (visit[to]) continue;
        dfs(E, to);
    }
}

int main(){

    int N, a, b, idx, from;
    cin >> N;
    queue<int> que;
    vector<int> deg(N);
    cycle.resize(N, 1);
    vector<vector<pair<int, int>>> E(N);

    for (int i=1; i<=N; i++){
        cin >> a >> b; a--; b--;
        E[a].push_back({b, i});
        E[b].push_back({a, i});
        deg[a]++; deg[b]++;
    }

    for (int i=0; i<N; i++){
        if (deg[i] == 1) que.push(i);
    }

    while(!que.empty()){
        from = que.front();
        que.pop();
        cycle[from] = 0;
        for (auto [to, idx] : E[from]){
            deg[to]--;
            if (deg[to] == 1) que.push(to);
        }
    }

    visit.resize(N);

    for (int i=0; i<N; i++){
        if (cycle[i] && !visit[i]) dfs(E, i);
    }

    cout << st.size() << endl;
    for (auto x : st) cout << x << " ";
    cout << endl;

    return 0;
}