// UUID: aed12377-f119-4ea6-b4ff-bfeccc00e164
#include <bits/stdc++.h>
using namespace std;

#define int long long
#define pii pair<int, int>
#define fi first
#define se second

vector<pii> elek;
vector<int> cs, v;
vector<vector<int>> adj;
queue<int> q;

void refresh(int x) {
    v[x]=0;
    for (int u : adj[x]) {
        v[x]+=(cs[x]==cs[u]);
    }
}

signed main() {
	int n;
    cin >> n;
    cs.resize(n+1);
    v.resize(n+1);
    adj.resize(n+1);
    for (int i = 1; i <= n/2; i++) {
        cs[i]=1;
    }
    for (int i = 1; i <= n; i++) {
        int u;
        cin >> u;
        while (u!=0) {
            if (u>i) {
                adj[i].push_back(u);
                adj[u].push_back(i);
                elek.push_back({i, u});
            }
            cin >> u;
        }
    }
    for (int i = 1; i <= n; i++) {
        refresh(i);
        if (v[i]>1)q.push(i);
    }
    while (!q.empty()) {
        int x = q.front();
        q.pop();
        cs[x]=!cs[x];
        refresh(x);
        for (int u : adj[x]) {
            refresh(u);
            if (v[u]>1)q.push(u);
        }
    }
    int m = 0;
    vector<int> ansv;
    for (int i = 1; i <= n; i++) {
        if (cs[i]==0) {
            m++;
            ansv.push_back(i);
        }
    }
    cout << m << endl;
    for (int x : ansv)cout << x << ' ';
}