// UUID: 1b03427f-bb55-4278-b355-c0d15b3c7d2f
#include <bits/stdc++.h>
using namespace std;

const int MAXN = 300'001;

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

void dfs(int u) {
    for (int v : g[u]) {
        if (col[v] == -1) {
            col[v] = col[u] ^ 1;
            dfs(v);
        }
    }
}

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

    for (int i = 1; i <= n; i++) {
        if (col[i] != -1) continue;
        queue<int> q;
        q.push(i);
        col[i] = 0;
        while (!q.empty()) {
            int u = q.front(); q.pop();
            for (int v : g[u]) {
                if (col[v] == -1) {
                    col[v] = col[u] ^ 1;
                    q.push(v);
                }
            }
        }
    }

    for (int i = 1; i <= n; i++) {
        int cnt = 0;
        for (int j : g[i]) {
            if (col[i] == col[j]) cnt++;
        }
        if (cnt > 1) col[i] ^= 1;
    }

    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;
}