#include <bits/stdc++.h>

using namespace std;
ifstream fin("interclasari.in");
ofstream fout("interclasari.out");
int n;
vector<int> rez;

inline vector<int> reuniune(vector<int> &a, vector<int> &b) {
    vector<int> c;
    int i = 0, j = 0;
    int n = a.size(), m = b.size();
    while(i < n && j < m) {
        if(a[i] <= b[j]) c.push_back(a[i++]);
        else c.push_back(b[j++]);
    }
    while(i < n) c.push_back(a[i++]);
    while(j < m) c.push_back(b[j++]);
    return c;
}

int main()
{
    int tt; fin >> tt >> n;
    for(int i=1; i<=n; i++) {
        int x; fin >> x;
        rez.push_back(x);
    }
    for(int i=2; i<=tt; i++) {
        fin >> n;
        vector<int> v;
        for(int j=1; j<=n; j++) {
            int x; fin >> x;
            v.push_back(x);
        }
        rez = reuniune(rez, v);
    }
    fout << rez.size() << '\n';
    for(int i : rez) fout << i << " ";

    return 0;
}