#include <algorithm>
#include <cmath>
#include <iomanip>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <tuple>
#include <vector>
using namespace std;
using ll = int64_t;
#define rep(i, j, n) for (int i = j; i < (n); ++i)
#define rrep(i, j, n) for (int i = (n)-1; j <= i; --i)

int main() {
  int n, a, b;
  cin >> n;
  vector<set<pair<int, int>>> g(n);
  vector<int> deg(n);
  rep(i, 0, n) {
    cin >> a >> b;
    --a, --b;
    g[a].insert({b, i});
    g[b].insert({a, i});
    deg[a]++;
    deg[b]++;
  }

  queue<int> q;
  rep(i, 0, n) if (deg[i] == 1) q.push(i);

  set<int> st;
  rep(i, 0, n) st.insert(i);
  while (!q.empty()) {
    int v = q.front();
    q.pop();
    auto [nv, idx] = *g[v].begin();
    --deg[nv];
    st.erase(idx);
    g[nv].erase({v, idx});
    if (deg[nv] == 1) q.push(nv);
  }

  cout << st.size() << '\n';
  for (auto itr = st.begin(); itr != st.end(); ++itr) cout << *itr + 1 << ' ';
  return 0;
}