#include <bits/stdc++.h>
using namespace std;

/*^ debug  */

template <typename A, typename B> string to_string(pair<A, B> p);
template <typename A, typename B, typename C> string to_string(tuple<A, B, C> p);
template <typename A, typename B, typename C, typename D> string to_string(tuple<A, B, C, D> p);
string to_string(const string& s) { return '"' + s + '"'; }
string to_string(const char* s) { return to_string((string) s); }
string to_string(bool b) { return (b ? "true" : "false"); }
string to_string(vector<bool> v) {
  bool first = true;
  string res = "{";
  for (int i = 0; i < static_cast<int>(v.size()); i++) {
    if (!first) { res += ", "; }
    first = false;
    res += to_string(v[i]);
  }
  res += "}";
  return res;
}
template <size_t N>
string to_string(bitset<N> v) {
  string res = "";
  for (size_t i = 0; i < N; i++) { res += static_cast<char>('0' + v[i]); }
  return res;
}
template <typename A>
string to_string(A v) {
  bool first = true;
  string res = "{";
  for (const auto &x : v) {
    if (!first) { res += ", "; }
    first = false;
    res += to_string(x);
  }
  res += "}";
  return res;
}
template <typename A, typename B>
string to_string(pair<A, B> p) { return "(" + to_string(p.first) + ", " + to_string(p.second) + ")"; }
template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p) { return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " + to_string(get<2>(p)) + ")"; }
template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p) { return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " + to_string(get<2>(p)) + ", " + to_string(get<3>(p)) + ")"; }
void debug_out() { cerr << endl; }
template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) { cerr << " " << to_string(H); debug_out(T...); }
#ifdef LOCAL
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif

/*  debug $*/

/*^ generic definitions  */

template<typename F>
struct _RecurFun : F {
  _RecurFun(F&& f) : F(forward<F>(f)) {}
  template<typename... Args>
  decltype(auto) operator()(Args&&... args) const { return F::operator()(*this, forward<Args>(args)...); }
};
template<typename F>
decltype(auto) RecurFun(F&& f) { return _RecurFun<F> { forward<F>(f) }; }

template<typename D, typename R>
vector<R> maps(const vector<D> &&d, function<R(D)> f) {
  vector<R> r(d.size());
  for (int i = 0; i < (int) d.size(); ++i) r[i] = f(d[i]);
  return r;
}

/*  generic definitions $*/

template<typename T>
struct Compress {
  vector<T> dat;
  Compress() {}
  Compress(vector<T> d) : dat(d) {
    sort(dat.begin(), dat.end());
    dat.erase(unique(dat.begin(), dat.end()), dat.end());
  }
  int operator()(const T &v) { return lower_bound(dat.begin(), dat.end(), v) - dat.begin(); }
  T operator[](int x) { return dat[x]; }
  int size() { return dat.size(); }
};

vector<int> topoSort(const vector<vector<int>> &g) {
  vector<int> deg(g.size()); {
    for (int u = 0; u < (int) g.size(); ++u) {
      for (int v : g[u]) ++deg[v];
    }
  }
  
  vector<int> res; {
    queue<int> que;
    for (int u = 0; u < (int) g.size(); ++u) if (deg[u] == 0) que.push(u);
    while (que.size()) {
      int u = que.front();
      que.pop();
      res.push_back(u);
      for (int v : g[u]) if (--deg[v] == 0) que.push(v);
    }
  }

  if (res.size() != g.size()) return vector<int>(); // no solution

  return res;
}

int main() {
  ios::sync_with_stdio(false);

  int N; { cin >> N; }

  vector<vector<int>> S(N); {
    for (int i = 0; i < N; ++i) {
      int D; { cin >> D; }
      S[i].resize(D);
      for (int j = 0; j < D; ++j) {
        cin >> S[i][j];
      }
    }
  }

  vector<int> nodes; {
    for (int i = 0; i < N; ++i) {
      for (int u : S[i]) nodes.push_back(u);
    }
    sort(nodes.begin(), nodes.end());
    nodes.erase(unique(nodes.begin(), nodes.end()), nodes.end());
  }

  Compress nodeMap(nodes);

  vector<vector<int>> G(nodeMap.size()); {
    for (int i = 0; i < N; ++i) {
      if (S[i][0] != S[i].back()) {
        G[nodeMap(S[i][0])].push_back(nodeMap(S[i].back()));
      }
    }
  }

  vector<int> res = maps<int, int>(topoSort(G), [&](int u) { return nodeMap[u]; });

  cout << res.size() << endl;
  for (int i = 0; i < (int) res.size(); ++i) cout << res[i] << " \n"[i+1 == (int) res.size()];
}