//Code by Patcas Csaba

#include <vector>
#include <string> 
#include <set> 
#include <map> 
#include <queue> 
#include <bitset> 
#include <stack>
#include <list>

#include <numeric> 
#include <algorithm> 

#include <cstdio>
#include <fstream>
#include <iostream> 
#include <sstream> 
#include <iomanip>

#include <cctype>
#include <cmath> 
#include <ctime>
#include <cassert>

using namespace std;

#define LL long long
#define PII pair <int, int>
#define VB vector <bool>
#define VI vector <int>
#define VD vector <double>
#define VS vector <string>
#define VPII vector <pair <int, int> >
#define VVI vector < VI >
#define VVB vector < VB >

#define FORN(i, n) for(int i = 0; i < (n); ++i)
#define FOR(i, a, b) for(int i = (a); i <= (b); ++i)
#define FORD(i, a, b) for(int i = (a); i >= (b); --i)
#define FORI(it, X) for(__typeof((X).begin()) it = (X).begin(); it !=(X).end(); ++it) 
#define REPEAT do{ 
#define UNTIL(x) }while(!(x)); 

#define SZ size()
#define BG begin() 
#define EN end() 
#define CL clear()
#define X first
#define Y second
#define RS resize
#define PB push_back
#define MP make_pair
#define ALL(x) x.begin(), x.end()

#define IN_FILE "a.in"
#define OUT_FILE "a.out"

int n = 0;
VS a;
map <char, set<int> > pos;
string sol;

bool found(string s)
{
	int curPos = -1;
	FORN(i, s.SZ)
	{
		if (!pos.count(s[i])) return false;
		set<int>::iterator it = pos[s[i]].lower_bound(curPos);
		if (it!=pos[s[i]].EN) curPos = *it;
	}
	return true;
}

int main()
{
	//Read data
	//freopen(IN_FILE, "r", stdin);
	//freopen(OUT_FILE, "w", stdout);

	//Solve
	string s;
	a.PB("dummy");
	while (cin >> s)
	{
		++n;
		a.PB(s);
	}

	string bestSol = "";

	FOR(i, 1, 10)
	{
		sol = a[1];
		FORN(i, sol.SZ)
		{
			pos[sol[i]].insert(i);
		}
		FOR(i, 2, n)
		{
			if (found(a[i])) continue;
			FORN(j, a[i].SZ)
			{
				pos[a[i][j]].insert(sol.SZ + j);
			}
			sol = sol + a[i];
		}

		if (bestSol.SZ == 0 || bestSol.SZ > sol.SZ) bestSol = sol;
		pos.clear();
		sol = "";
		random_shuffle(a.BG + 1, a.EN);
	}
	//Write data
	cout << bestSol << endl;

	return 0;
}