// UUID: 9bed5cca-b4f0-455f-972e-af026faa2e0c
#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) {
            col[i] = 0;
            dfs(i);
        }
    }

    vector<int> ord(n);
    iota(ord.begin(), ord.end(), 1);
    random_shuffle(ord.begin(), ord.end());
    bool g = true;
    for (int i : ord) {
        int cnt = 0;
        for (int j : g[i]) {
            if (col[i] == col[j]) cnt++;
        }
        if (cnt > 1) g = false;
    }
    assert(g);

    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;
}