#include <fstream>
#define DIM 1000010
using namespace std;
int n,m,i,j,q,t,k;
int v[DIM],w[DIM],r[DIM];
int main (){
    ifstream fin ("interclasari.in");
    ofstream fout ("interclasari.out");
    fin>>q;
    fin>>n;
    for (i=1;i<=n;i++){
        fin>>v[i];
    }
    for (t=2;t<=q;t++){
        fin>>m;
        for (i=1;i<=m;i++)
            fin>>w[i];
        i=1;
        j=1;
        k=0;
        while (i<=n&&j<=m){
            if (v[i]<w[j]){
                r[++k]=v[i];
                i++;
            }
            else{
                r[++k]=w[j];
                j++;
            }
        }
        for (;i<=n;i++){
            r[++k]=v[i];
        }
        for (;j<=m;j++){
            r[++k]=w[j];
        }
        for (i=1;i<=k;i++)
            v[i]=r[i];
        n=k;
    }
    fout<<n<<"\n";
    for (i=1;i<=n;i++){
        fout<<r[i]<<" ";
    }
}