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

typedef long long ll;
typedef pair< int, int > pii;
typedef vector< int > vi;
typedef vector< vi > vvi;
typedef vector< ll > vl;
typedef vector< vl > vvl;
typedef vector< pii > vp;
typedef vector< vp > vvp;
typedef vector< string > vs;
typedef vector< double > vd;
typedef vector< vd > vvd;

template< class T1, class T2 >
int upmin( T1 &x, T2 v ){
  if( x > v ){
    x = v;
    return 1;
  }
  return 0;
}

template< class T1, class T2 >
int upmax( T1 &x, T2 v ){
  if( x < v ){
    x = v;
    return 1;
  }
  return 0;
}

const int INF = 0x3f3f3f3f;

int N;
priority_queue< string, vector< string >, greater< string > > pq;

void init(){
  cin >> N;
  for( int i = 0; i < N; ++i ){
    string s; cin >> s;
    pq.emplace( s );
  }
}

void preprocess(){
  
}

void solve(){
  while( not pq.empty() ){
    string s = pq.top(); pq.pop();
    cout << s[ 0 ];
    s = s.substr( 1 );
    if( s.empty() ) continue;
    pq.emplace( s );
  }
  cout << endl;
}

signed main(){
  ios::sync_with_stdio( 0 );
  init();
  preprocess();
  solve();
  return 0;
}