#include <iostream>
#include <vector>
#include <set>

using namespace std;

int main()
{
    int n;
    cin >> n;
    vector <string> palabras(n);

    for(int i=0; i<n; i++)
        cin >> palabras[i];

    vector <set<string> > palabrasPorLetra(30);
    vector <int> cantPorLetra(30, 0);

    int maxRep = 0;

    for(int i=0; i<n; i++)
    {
        char a = palabras[i][0];
        char b = palabras[i].back();

        palabrasPorLetra[a-'a'].insert(palabras[i]);

        if(palabras[i].size() > 1)
        {
            palabrasPorLetra[b-'a'].insert(palabras[i]);
            cantPorLetra[b-'a']++;
        }

        maxRep = max(maxRep, cantPorLetra[a-'a']);
        maxRep = max(maxRep, cantPorLetra[b-'a']);
    }

    vector <char> letrasRta;
    vector <string> palabrasRta;

    for(int i=0; i<30; i++)
    {
        if(cantPorLetra[i] == maxRep)
        {
            letrasRta.push_back(i+'a');
            for(string pal:palabrasPorLetra[i])
                palabrasRta.push_back(pal);
        }
    }

    for(int i=0; i<letrasRta.size(); i++)
        cout << letrasRta[i] << " ";
    cout << endl;

    for(int i=0; i<palabrasRta.size(); i++)
        cout << palabrasRta[i] << endl;

    return 0;
}