#include <bits/stdc++.h>
//#include <ext/pb_ds/assoc_container.hpp>
//#include <ext/pb_ds/tree_policy.hpp>
//#include <ext/pb_ds/detail/standard_policies.hpp>

using namespace std;
//using namespace __gnu_pbds;

#define F first
#define S second
#define pb push_back
//#define mt make_tuple
//#define mp make_pair

typedef long long ll;

//typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update> ordered_set;

const int rx[4] = {-1, 1, 0, 0};
const int ry[4] = {0, 0, 1, -1};

const int N = 100100;

unordered_map<int, int> mp;
vector<pair<int, int>> e;
vector<int> g[N];
int p[N];
int n;
vector<pair<int, int>> ans;

void dfs(int v, int pr = -1){
  while (p[v] < g[v].size()){
     int i = p[v];
    if (mp.count(g[v][i]) == 1){
      p[v]++;
      continue;
    }
    mp[g[v][i]] = 1;
    int to = (e[g[v][i]].F == v ? e[g[v][i]].S : e[g[v][i]].F);
    p[v]++;
    dfs(to, v);
  }
  if (pr != -1){
    ans.pb({pr, v});
  }
}

#define FILE "euler"
int main() {
  ios_base::sync_with_stdio(0);
#ifdef LOCAL
  freopen("input.txt", "r", stdin);
//  freopen("output.txt", "w", stdout);
#else
  freopen(FILE".in", "r", stdin);
  freopen(FILE".out", "w", stdout);
#endif // LOCAL
  mp.reserve(300000);
  mp.max_load_factor(0.25);
  scanf("%d", &n);
  for (int i = 0; i < n; i++){
    int k;
    scanf("%d", &k);
    while (k--){
      int x;
      scanf("%d", &x);
      if (x - 1 < i) continue;
      e.pb({i, x - 1});
      g[i].pb(e.size() - 1);
      g[x - 1].pb(e.size() - 1);
    }
    p[i] = 0;
  }
  vector<int> _ch;
  for (int i = 0; i < n; i++){
    if (g[i].size() % 2 == 1){
      _ch.pb(i);
    }
  }
  if (_ch.size() != 0 && _ch.size() != 2){
    printf("-1\n");
    return 0;
  }
  bool rev = false;
  int start = 0;
  if (_ch.size() == 2){
    rev = true;
    int a = _ch[_ch.size() - 1];
    int b = _ch[_ch.size() - 2];
    start = a;
    vector<bool> bad(g[a].size(), false);
    int p = 0;
    for (int x : g[a]){
      if (e[x].F == b || e[x].S == b){
        bad[p] = true;
      }
      p++;
    }
    vector<int> cur = g[a];
    g[a].clear();
    for (int i = 0; i < cur.size(); i++){
      if (!bad[i]){
        g[a].pb(cur[i]);
      }
    }
    for (int i = 0; i < cur.size(); i++){
      if (bad[i]){
        g[a].pb(cur[i]);
      }
    }

//    e.pb({a, b});
//    g[a].pb(e.size() - 1);
//    swap(g[a][0], g[a].back());
//    g[b].pb(e.size() - 1);
//    swap(g[b][0], g[b].back());
  }
  dfs(start);
  reverse(ans.begin(), ans.end());
//  if (rev) {
//    ans.pop_back();
//  }
  printf("%d\n", ans.size());
  for (auto to : ans) printf("%d ", to.F + 1);
  printf("%d ", ans.back().S + 1);


//#ifdef LOCAL
//  cerr << "TIME = " << fixed << 1.0 * clock() / CLOCKS_PER_SEC << endl;
//#endif // LOCAL
  return 0;
}