#include <bits/stdc++.h>

typedef long long ll;
typedef unsigned long long ull;

#define FOR(i,a,b) for(int (i)=(a);i<(b);i++)
#define REP(i,n) FOR(i,0,n)
#define RANGE(vec) (vec).begin(),(vec).end()

using namespace std;


class MergeAndLexicographicOrderSort
{
public:
    void solve(void)
    {
            int N;
            cin>>N;

            auto lex_comp = [](string a, string b) {
                int n = max(a.length(), b.length());
                a += string(n-a.length(),'~');
                b += string(n-b.length(),'~');
                return b<a;
            };
            priority_queue<string,vector<string>,decltype(lex_comp)> S(lex_comp);
            REP(i,N)
            {
                string s;
                cin>>s;
                S.push(s);
            }

            string T;
            while (!S.empty())
            {
                string s = S.top();
                S.pop();
                T += s[0];
                s = s.substr(1);
                if (s.length() > 0)
                    S.push(s);
            }
            cout<<T<<endl;
    }
};

#if 1
int main(int argc, char *argv[])
{
        ios::sync_with_stdio(false);
        auto obj = new MergeAndLexicographicOrderSort();
        obj->solve();
        delete obj;
        return 0;
}
#endif