#include using namespace std; using graph = vector>; vector dfs(int v, int p, vector &visited, const graph &to, vector route) { visited.at(v) = true; for (int next : to.at(v)) { if (next == p) continue; route.push_back(v); if (visited.at(next)) { route.push_back(next); return route; } auto res = dfs(next, v, visited, to, route); if (not res.empty()) return res; route.pop_back(); } return {}; } int main() { int n; cin >> n; vector a(n), b(n); for (int i = 0; i < n; i++) { cin >> a.at(i) >> b.at(i); a.at(i)--; b.at(i)--; } graph to(n); for (int i = 0; i < n; i++) { to.at(a.at(i)).push_back(b.at(i)); to.at(b.at(i)).push_back(a.at(i)); } vector route; vector visited(n); auto res = dfs(0, -1, visited, to, route); int s = res.back(); res.pop_back(); reverse(res.begin(), res.end()); vector inloop(n); for (int v : res) { inloop.at(v) = true; if (v == s) break; } cout << count(inloop.begin(), inloop.end(), true) << endl; for (int i = 0; i < n; i++) { if (inloop.at(a.at(i)) and inloop.at(b.at(i))) { cout << i + 1 << " "; } } cout << endl; }