#include<cstring>
#include<cstdio>
#include<iostream>
#include<algorithm>
using namespace std;

const int maxn=1e3+10;
int n;

struct String{
	char s[210];
	int length;
}ch[maxn];

bool cmp(String,String);

int main(){
	freopen("brick.in","r",stdin);
	freopen("brick.out","w",stdout);
	int i; 
	cin>>n;
	for(i=1;i<=n;i++){
		scanf("%s",ch[i].s);
		ch[i].length=strlen(ch[i].s);
	}
	sort(ch+1,ch+n+1,cmp);
	for(i=1;i<=n;i++)
		cout<<ch[i].s;
}

bool cmp(String a,String b){
	int i;
	int minl=min(a.length,b.length);
	for(i=0;i<minl;i++){
		if(a.s[i]>b.s[i])
			return 1;
		else if(a.s[i]<b.s[i])
			return 0;
	}
	if(a.length==b.length)return 1;
	if(a.length>b.length){
		if(a.s[minl-1]>=b.s[0])
			return 1;
		else return 0;
	}
	if(b.length<a.length){
		if(b.s[minl-1]>=a.s[0])
			return 0;
		else return 1;
	}
}