#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <queue>
#include <string>
#include <map>
#include <set>
#include <stack>
#include <tuple>
#include <deque>
#include <array>
#include <numeric>
#include <bitset>
#include <iomanip>
#include <cassert>
#include <chrono>
#include <random>
#include <limits>
#include <iterator>
#include <functional>
#include <sstream>
#include <fstream>
#include <complex>
#include <cstring>
#include <unordered_map>
#include <unordered_set>
using namespace std;

using ll = long long;
constexpr int INF = 1001001001;
constexpr int mod = 1000000007;
// constexpr int mod = 998244353;

template<class T>
inline bool chmax(T& x, T y){
    if(x < y){
        x = y;
        return true;
    }
    return false;
}
template<class T>
inline bool chmin(T& x, T y){
    if(x > y){
        x = y;
        return true;
    }
    return false;
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int N;
    cin >> N;
    vector<string> S(N);
    for(int i = 0; i < N; ++i){
        cin >> S[i];
        S[i] += '{';
    }
    using node = tuple<char, char, int, int>;
    priority_queue<node, vector<node>, greater<node>> que;
    for(int i = 0; i < N; ++i){
        que.emplace(S[i][0], S[i][1], i, 0);
    }
    string ans = "";
    while(!que.empty()){
        auto [c, cc, i, j] = que.top();
        que.pop();
        ans += c;
        if(cc != '{')   que.emplace(S[i][j + 1], S[i][j + 2], i, j + 1);
    }
    cout << ans << endl;

    return 0;
}