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

int main() {

    ios_base::sync_with_stdio(false);
    cin.tie(0);

    int n; cin >> n;
    vector<vector<int>> adj(n);
    vector<int> state(n, -1);
    vector<int> hate(n, 0);
    for (int i = 0; i < n; i++) {
        state[i] = i%2;
        int e;
        while (cin >> e) {
            if (e == 0) break;
            e--;
            adj[i].push_back(e);
        }
    }

    set<int> bad;
    for (int i = 0; i < n; i++) {
        for (const int& e : adj[i]) {
            if (state[i] == state[e]) {
                hate[i]++;
            }
        }
        if (hate[i] >= 2) bad.insert(i);
    }
    
    int e = *bad.begin();
    while (!bad.empty()) {
        state[e] = (state[e] == 0) ? 1 : 0;
        for (const int& m : adj[e]) {
            if (state[e] == state[m]) {
                hate[e]++; hate[m]++;
            } else {
                hate[e]--; hate[m]--;
            }
        }
        if (hate[e] < 2) bad.erase(e);
        for (int& m : adj[e]) {
            if (hate[m] < 2) {
                bad.erase(m);
            } else {
                bad.insert(m);
            }
        }
    }

    vector<int> res;
    for (int i = 0; i < n; i++) {
        if (state[i] == 0) res.push_back(i+1);
    }

    cout << res.size() << "\n";
    for (int i : res) cout << i << " ";
	
    return 0;
}