#include <fstream>

using namespace std;

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

int k,n,i,j,l,a[20000005],b[1000005],sol[20000005];

int main()
{
    fin >> k;
    fin >> n;
    for (i=1; i<=n; i++)
        fin >> a[i];
    int lung1 = n;
    for (l=2; l<=k; l++)
    {
        fin >> n;
        for (i=1; i<=n; i++)
            fin >> b[i];
        int lung2 = n;
        i = 1;
        j = 1;
        int t = 0;
        while (i <= lung1 && j <= lung2)
        {
            if (a[i] < b[j])
            {
                sol[++t] = a[i];
                i++;
            }
            else
            {
                sol[++t] = b[j];
                j++;
            }
        }
        while (i <= lung1)
        {
            sol[++t] = a[i];
            i++;
        }
        while (j <= lung2)
        {
            sol[++t] = b[j];
            j++;
        }
        for (i=1; i<=t; i++)
            a[i] = sol[i];
        lung1 = t;
    }
    fout << lung1 << "\n";
    for (i=1; i<=lung1; i++)
        fout << sol[i] << " ";
    return 0;
}