#include <bits/stdc++.h>
#define NMAX 25
#define INF 99999999
using namespace std;

ifstream fin("interclasari.in");
ofstream fout("interclasari.out");

vector<int> v[NMAX];
int k, n, x, ok=1;
int poz[NMAX];
vector <int> aux;
int minCurent;
int lineMin;

int main()
{
    fin >> k;
    for (int i=0; i<k; i++)
    {
        fin >> n;
        for (int j=0; j<n; j++)
        {
            fin >> x;
            v[i].push_back(x);
        }
    }
    while(ok)
    {
        ok = 0;
        minCurent = INF;
        for (int i=0; i<k; i++)
        {
            if (poz[i] < v[i].size())
            {
                if (minCurent > v[i][poz[i]])
                {
                    ok = 1;
                    minCurent = v[i][poz[i]];
                    lineMin = i;
                }
            }
        }
        if (ok)
        {
            aux.push_back(v[lineMin][poz[lineMin]]);
            poz[lineMin]++;
        }
    }
    fout << aux.size() << '\n';
    for (unsigned i=0; i<aux.size(); i++)
    {
        fout << aux[i] << " ";
    }
    return 0;
}