#include<iostream>
#include<algorithm>
using namespace std;
bool cmp(string a,string b){
	for(int i=0;i<min(a.length(),b.length());i++){
		if(a[i]-'0'<b[i]-'0')return 0;
		if(b[i]-'0'<a[i]-'0')return 1;
	}
	return a.length()<b.length();
}
int main(){
	int n;string a[20];
	cin>>n;for(int i=0;i<n;i++)cin>>a[i];
	sort(a,a+n,cmp);
	for(int i=0;i<n;i++)cout<<a[i];
	return 0;
}