#include <bits/stdc++.h>

using namespace std;
using ll = long long;
using VI = vector<int>;
using VL = vector<ll>;
using PII = std::pair<int, int>;
using PLL = std::pair<ll, ll>;

#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define repr(i, n) for (int i = (int)(n)-1; i >= 0; i--)
#define rep2(i, s, n) for (int i = (s); i < (int)(n); i++)
#define allpt(v) (v).begin(), (v).end()
#define allpt_c(v) (v).cbegin(), (v).cend()
#define allpt_r(v) (v).rbegin(), (v).rend()



const int mod = 1e9 + 7;
const string wsp = " ";
const string tb = "\t";
const string rt = "\n";

template <typename T>
void show1dvec(vector<T> v)
{
    if (v.size() == 0)
        return;
    int n = v.size() - 1;
    rep(i, n) cout << v[i] << wsp;
    cout << v[n] << rt;
    return;
}

template <typename T>
void show2dvec(vector<vector<T>> v)
{
    int n = v.size();
    rep(i, n) show1dvec(v[i]);
}



int main()
{

#ifdef DEBUG
    cout << "DEBUG MODE" << endl;
    ifstream in("input.txt"); //for debug
    cin.rdbuf(in.rdbuf());    //for debug
#endif

    int n, m = 0;
    cin >> n;
    string t;
    vector<string> vs(n);
    vector<pair<string, int>> q;
    rep(i, n)
    {
        cin >> vs[i];
        m += vs[i].length();
        vs[i] += 'z';
    }

    rep(i, m)
    {
        q.clear();
        rep(j, n)
        {
            if (vs[j].length() > 1)
            {
                q.push_back(make_pair(vs[j], j));
            }
        }

        sort(allpt(q));

        t += q[0].first[0];
        vs[q[0].second] = vs[q[0].second].substr(1, vs[q[0].second].length() - 1);

        
    }

    cout << t << rt;

    return 0;
}