#include <iostream>
#include <algorithm>
#include <iomanip>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <numeric>
#include <bitset>
#include <cmath>

static const int MOD = 1000000007;
using ll = long long;
using u32 = uint32_t;
using namespace std;

template<class T> constexpr T INF = ::numeric_limits<T>::max() / 32 * 15 + 208;

template <typename T>
using GPQ = priority_queue<T, vector<T>, greater<T>>;

int main() {
    int n;
    cin >> n;
    GPQ<string> Q;
    for (int i = 0; i < n; ++i) {
        string s;
        cin >> s;
        s += 127;
        Q.emplace(s);
    }
    string ans;
    while(!Q.empty()){
        string s = Q.top(); Q.pop();
        if(s.front() != 127){
            ans += s.front();
            s = s.substr(1, 100);
            Q.emplace(s);
        }
    }
    cout << ans << "\n";
    return 0;
}