#include<bits/stdc++.h>
#define rep(i,a,b) for(int i=int(a);i<int(b);++i)
using namespace std;
typedef long long ll;
int INF = (1LL << 30) - 1;
int MOD = 1e9+7;
bool comp(const string &a, const string &b){
    int i;
    for(i = 0;i < min(a.size(), b.size()); i++){
        if(a[i] != b[i])return a[i] < b[i];
    }
    if(a.size() > b.size())return a[i-1] < a[i];
    else                   return b[i-1] < b[i];
}
main(){
    int N;
    cin >> N;
    //priority_queue<string, vector<string>, comp() > que;
    priority_queue<string, vector<string>, greater<string> > que;
    /*
    priority_queue<string, vector<string>, function<bool(string, string) > >
    que(
        [](string a, string b){
            int i;
            for(i = 0;i < min(a.size(), b.size()); i++){
                if(a[i] != b[i])return a[i] > b[i];
            }
            if(a.size() > b.size())return a[i-1] <= a[i];
            else                   return b[i-1] <= b[i];
        }
    );
    */
    rep(i,0,N){
        string s;
        cin >> s;
        que.push(s);
    }
    string ans;
    while(!que.empty()){
        auto str = que.top();
        que.pop();
        if(str.length() != 0){
            ans.push_back(str[0]);
            que.push(str.substr(1));
        }
    }
    cout << ans << endl;
}