#include <bits/stdc++.h>

#define MOD 1000000007
#define pe(str) return cout<<(str)<<endl,0
#define px(str) cout<<(str)<<endl,exit(0)
#define accu(ac,v) cout<<setprecision(ac)<<v<<endl
#define pr(str) cout<<(str)<<endl
#define prpr(str) cout<<str<<endl
#define db(str) cerr<<"debug:"<<(str)<<endl
#define dbdb(str) cerr<<"debugs:"<<str<<endl
#define re(i,n) for(int i=0;i<(n);i++)
#define rre(i,n) for(int i=(n);i>=0;i--)
#define rep(i,a,b) for(int i=(a);i<(b);i++)
#define rrep(i,a,b) for(int i=(b);i>=(a);i--)
#define bw(a,b,c) (((a)<=(b))&&((b)<=(c)))
#define hello cout<<"hello"<<endl
#define spre(a) setprecision(a)
#define all(a) a.begin(),a.end()
#define rall(a) a.rbegin(),a.rend()
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<int,int> pii;
typedef complex<int> point;

template<class InputIterator>
void dump(InputIterator first,InputIterator last,char delim=' '){
	for(InputIterator it=first;it!=last;it++){
		if(it!=first)cout<<delim;
		cout<<*it;
	}
}

ull p(ull x,ull y){
	if(y==0) return 1;
	ull A=p(x,y/2)%MOD;
	return (y&1?((A*A)%MOD*x)%MOD: (A*A)%MOD);
	// return (y&1?((A*A)*x):(A*A));
}

template<class T>
void swp(T &a,T &b){
	T t=a; a=b; b=t;
}

int main(void){
	int n,len=0;
	cin>>n;
	string s[n];
	int a=0,b=999;
	re(i,n)cin>>s[i],len+=s[i].size();
	string t="";
	while(1){
		a=n-1;
		re(i,n-1) if(s[i][0]<s[a][0])a=i;
		if(s[a][0]==127)break;
		t+=s[a][0];
		if(s[a].size()!=1)s[a]=s[a].substr(1);
		else s[a][0]=127;
	}
	cout<<t<<endl;
	return 0;
}