// UUID: d94981ce-fa79-4438-a08a-8992d28e186f
#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);
            g[x].emplace_back(i);
            cin >> x;
        }
    }
    for (int i = 1; i <= n; i++) {
        if (col[i] == -1) {
            col[i] = 0;
            dfs(i);
        }
    }
    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;
}