// UUID: 40a868da-62a0-4af9-ac27-f85d1b3c5833
#include <bits/stdc++.h>
using namespace std;

const int MAXN = 300'001;

int col[MAXN];
vector<int> g[MAXN];

void solve() {
    int n; cin >> n;
    fill(col, col+MAXN, 0);
    for (int i = 1; i <= n; i++) {
        int x; cin >> x;
        while (x) {
            g[i].emplace_back(x);
            cin >> x;
        }
    }

    stack<int> st;
    for (int i = 1; i <= n; i++) st.push(i);

    while (!st.empty()) {
        int i = st.top(); st.pop();
        int cnt = 0;
        for (int j : g[i]) {
            if (col[i] == col[j]) cnt++;
        }
        if (cnt > 1) {
            col[i] ^= 1;
            for (int j : g[i]) {
                if (col[i] != col[j]) st.push(j);
            }
        }
    }

    cout << count(col+1, col+n+1, 0) << "\n";
    for (int i = 1; i <= n; i++) {
        if (col[i] == 0) cout << i << " ";
    }
    cout << "\n";
}

int main() {
	ios::sync_with_stdio(0); cin.tie(0);
    int t = 1;
    // cin >> t;
    while (t--) solve();
    return 0;
}