#include <bits/stdc++.h>
using namespace std;

int main() {
	ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
	int n;
	cin >> n;
	vector<pair<int, int> > a(n+1);
	vector<int> b(n+1);
	for(int i = 1; i <= n; i++) {
        int x, y;
        cin >> x >> y;
        b[x]++, b[y]++;
        a[i] = {x, y};
	}

	queue<int> q;

	for(int i = 1; i <= n; i++) {
        if (b[i] < 2) q.push(i);
	}


	while(!q.empty()) {
        int t = q.front();
        q.pop();
        if (b[a[t].first] == 2) {
            b[a[t].first]--;
            q.push(a[t].first);
        } else if (b[a[t].first] > 2) {
            b[a[t].first]--;
        }

        if (b[a[t].second] == 2) {
            b[a[t].second]--;
            q.push(a[t].second);
        } else if (b[a[t].second] > 2) {
            b[a[t].second]--;
        }



	}

    vector<int> ans;

	for(int i = 1; i <= n; i++) if (b[i] > 1) ans.push_back(i);

	cout << ans.size() << '\n';
	for(int x : ans) cout << x << ' ';


	return 0;
}