#include "bits/stdc++.h"
using namespace std;

#define REP(i, n) for(int i=0; i<(n); i++)

int N,T;
class Comp {
public:
    bool operator()(string a, string b) {
        REP(i,a.size()) {
            if (a[i] == b[i]) continue;
            if (i >= b.size()) return false;
            return a[i] > b[i];
        }
        return true;
    }
};
signed main()
{
    cin >> N;
    string S;
    priority_queue<string, vector<string>, Comp> que;
    REP(i,N) {
        cin >> S;
        que.push(S);
    }
    string t = "";
    while(que.size()) {
        string s = que.top();
        que.pop();
        t += s[0];
        s.erase(s.begin());
        if (s.size()) que.push(s);
    }
    cout << t << endl;
    return 0;
}