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

struct rec
{
	int l;
	char info[300];
}num[1010];

void swaprec(rec& a,rec& b)
{
	rec temp;
	temp=a;
	a=b;
	b=temp;
}

int main(void)
{
	freopen("brick.in","r",stdin);
	freopen("brick.out","w",stdout);
	int i,j,n;
	cin>>n;
	for (i=1;i<=n;i++)
	{
		cin>>num[i].info;
		num[i].l=strlen(num[i].info);
		for (j=num[i].l;j<=210;j++)
			num[i].info[j]=num[i].info[j-1];
	}
	for (i=1;i<n;i++)
		for (j=1;j<=n-i;j++)
			if (strcmp(num[j].info,num[j+1].info)<=0)
				swaprec(num[j],num[j+1]);
	for (i=1;i<=n;i++)
	{
		num[i].info[num[i].l]='\0';
		cout<<num[i].info;
	}
	cout<<endl;
	return(0);
}