#include <bits/stdc++.h>
using namespace std;
using LL=long long;
using ULL=unsigned long long;
#define rep(i,n) for(int i=0; i<(n); i++)

int N;
vector<vector<int>> S;
vector<vector<int>> V;
vector<int> I;


const int Z=2000;
vector<int> appeared;

int main(){
  cin>>N;

  S.resize(N);
  appeared.assign(Z,0);
  rep(i,N){
    int d; cin>>d;
    S[i].resize(d);
    rep(j,d){ cin>>S[i][j]; S[i][j]--; appeared[S[i][j]]=1; }
  }

  V.resize(Z);
  I.assign(Z,0);
  rep(i,N){
    if(S[i].front()!=S[i].back()){
      V[S[i].front()].push_back(S[i].back());
      I[S[i].back()]++;
    }
  }

  queue<int> Q;
  rep(i,Z) if(I[i]==0) Q.push(i);
  vector<int> ans;
  while(Q.size()){
    int p=Q.front(); Q.pop();
    ans.push_back(p);
    for(int e:V[p]) if(--I[e]==0) Q.push(e);
  }

  if(ans.size()!=Z) cout<<0<<endl;
  else{
    vector<int> ans2;
    for(int a:ans) if(appeared[a]) ans2.push_back(a);
    cout<<ans2.size()<<endl;
    rep(i,ans2.size()){ if(i) cout<<" "; cout<<(ans2[i]+1); }
  }

  return 0;
}