#include <bits/stdc++.h>
//#include <chrono>
//#pragma GCC optimize("O3")
using namespace std;
#define reps(i,s,n) for(int i = s; i < n; i++)
#define rep(i,n) reps(i,0,n)
#define Rreps(i,n,e) for(int i = n - 1; i >= e; --i)
#define Rrep(i,n) Rreps(i,n,0)
#define ALL(a) a.begin(), a.end()
#define fi first
#define se second

using ll = long long;
using vec = vector<ll>;
using mat = vector<vec>;

ll N,M,H,W,Q,K,A,B;
string S;
typedef pair<ll, ll> P;
const ll INF = (1LL<<48);

struct edge{
    int to, id;
    edge(){}
    edge(int a, int b) : to(a), id(b){}
};
using ve = vector<edge>;

int main() {
    cin>>N;
    vector<ve> G(N, ve(0));
    vec num(N, 0);
    rep(i, N){
        int a, b; cin>>a>>b;
        --a, --b;
        G[a].emplace_back(b, i);
        G[b].emplace_back(a, i);
        ++num[a]; ++num[b];
    }
    vec ans(N, 1);
    queue<int> que;
    rep(i, N) if(num[i] == 1) que.push(i);
    while(!que.empty()){
        int v = que.front(); que.pop();
        for(edge &e : G[v]){
            if(ans[e.id]){
                ans[e.id] = 0;
                --num[e.to];
                if(num[e.to] == 1) que.push(e.to);
            }
        }
    }
    int sum = accumulate(ALL(ans), 0LL);
    cout<<sum<<endl;
    rep(i, N) if(ans[i]) cout<<i + 1 <<(--sum ? ' ' : '\n');
}