#include <cstdio>
#include <iostream>
#include <vector>
#include <map>
#include <set>
#include <string>
#include <cstring>
#include <sstream>
#include <algorithm>
#include <functional>
#include <queue>
#include <stack>
#include <cmath>
#include <iomanip>
#include <list>
#include <bitset>
using namespace std;
inline int toInt(string s) { int v; istringstream sin(s); sin >> v; return v; }
template<class T> inline string toString(T x) { ostringstream sout; sout << x; return sout.str(); }
template<class T> inline T sqr(T x) { return x*x; }
typedef pair<int, int> P;
typedef long long ll;
typedef unsigned long long ull;

#define For(i,a,b)	for(int (i) = (a);i < (b);(i)++)
#define rep(i,n)	For(i,0,n)
#define clr(a)		memset((a), 0 ,sizeof(a))
#define mclr(a)		memset((a), -1 ,sizeof(a))
#define all(a)		(a).begin(),(a).end()
#define rall(a)		(a).rbegin(), (a).rend()
#define sz(a)		(sizeof(a))
#define Fill(a,v)	fill((int*)a,(int*)(a+(sz(a)/sz(*(a)))),v)
#define fi first
#define se second
bool cheak(int x, int y, int xMax, int yMax){ return x >= 0 && y >= 0 && xMax > x && yMax > y; }
const int dx[4] = { -1, 0, 1, 0 }, dy[4] = { 0, 1, 0, -1 };
const int mod = 1000000007;
const int INF = 1e9;

int main()
{
	int n;
	cin >> n;
	vector<string> s(n);
	rep(i, n)cin >> s[i];
	rep(i, n)s[i] += ('z' + 1);

	string T;

	vector<int> t(n, 0);


	bool ef = false;
	while (!ef){
		ef = true;
		rep(i, n){
			if (s[i].size() != t[i]+1){
				ef = false; break;
			}
		}
		if (ef)break;
		vector<bool> f(n, true);

		bool nf = false;
		vector<int> tt = t;
		while (!nf){
			char Min = 'z'+1;
			rep(i, n){
				if (f[i] && Min > s[i][tt[i]]){
					Min = s[i][tt[i]];
				}
			}
			int sum = 0;
			rep(i, n){
				if (f[i] && Min == s[i][tt[i]]){
					tt[i]++;
					sum++;
				}
				else{
					f[i] = false;
				}
			}
			if (sum == 1){
				rep(i, n)if (f[i]){
					T += s[i][t[i]++]; nf = true; break;
				}
			}
		}
	}

	cout << T << endl;

	return 0;
}