#include <bits/stdc++.h>

using namespace std;

int main() {
    iostream::sync_with_stdio(0);
    cin.tie(0);
    int N;
    cin >> N;
    vector<vector<int>> edges(N, vector<int>());
    vector<int> invitee_counter(N, 0);
    for(int i = 0, a, b; i < N; ++i) {
        cin >> a >> b;
        --a;
        --b;
        edges[i].push_back(a);
        edges[i].push_back(b);
        ++invitee_counter[a];
        ++invitee_counter[b];
    }
    vector<int> nodes(N);
    for(int i = 0; i < N; i++) nodes[i] = i;
    while(true) {
        sort(nodes.begin(), nodes.end(), [&](int a, int b) {
            if(invitee_counter[a] == invitee_counter[b]) return a > b;
            return invitee_counter[a] > invitee_counter[b];
        });
        if(invitee_counter[*nodes.rbegin()] >= 2) break;
        for(auto it = nodes.rbegin(); it != nodes.rend(); ++it) {
            if(invitee_counter[*it] >= 2) break;
            for(int n : edges[*it]) --invitee_counter[n];
            nodes.pop_back();
        }
    }
    cout << nodes.size() << "\n";
    for(auto it = nodes.rbegin(); it != nodes.rend(); ++it) cout << (*it) + 1 << " ";
    cout << "\n";
    return 0;
}