#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
#include<cmath>
using namespace std;
int n;
char s[210];  int ls;
int a[1100][210],la[1100];
int rank[1100];
int tong[10][11000];
int max_len=0;
int main(){
	//freopen("ddd.in","r",stdin);
	freopen("brick.in","r",stdin);
	freopen("brick.out","w",stdout);
	cin>>n;
	for(int i=1;i<=n;i++){
		scanf("%s",s);  ls=strlen(s);
		la[i]=ls;
		max_len=max(max_len,ls);
		for(int j=0;j<ls;j++)  a[i][j]=s[j]-'0';
	}
	for(int i=1;i<=n;i++)  rank[i]=i;
	for(int t=max_len-1;t>=0;t--){
		for(int i=0;i<=9;i++)  tong[i][0]=0;
		for(int i=1;i<=n;i++)
			tong[a[rank[i]][t]][++tong[a[rank[i]][t]][0]]=rank[i];
		int _top=0;
		for(int i=0;i<=9;i++)
			for(int j=1;j<=tong[i][0];j++)
				rank[++_top]=tong[i][j];
	}
	for(int i=n;i>=1;i--)
		for(int j=0;j<la[rank[i]];j++)
			printf("%d",a[rank[i]][j]);
	cout<<endl;
	return 0;
}