#include <fstream>
#include <vector>
#include <climits>
using namespace std;
ifstream in("interclasari.in");
ofstream out("interclasari.out");
int k,k1,i,j,n,x,sir,v[21],b[20000010],minn=INT_MAX,elemente;
vector <int> a[21];
int main()
{
    in>>k;
    for (i=1; i<=k; ++i)
    {
        in>>n;
        if (n==0)
            v[i]=-1;
        elemente+=n;
        for (j=1; j<=n; ++j)
        {
            in>>x;
            a[i].push_back(x);
        }
    }
    for (i=1; i<=elemente; ++i)
    {
        for (j=1; j<=k; ++j)
        {
            if (v[j]>=0 && a[j][v[j]]<minn)
            {
                minn=a[j][v[j]];
                sir=j;
            }
        }
        v[sir]++;
        b[++k1]=minn;
        minn=INT_MAX;
    }
    out<<k1<<"\n";
    for (i=1; i<=k1; ++i)
        out<<b[i]<<" ";
}