#include <bits/stdc++.h>
using namespace std;

string a[25];

bool cmp(string x,string y){
	if(x.size() != y.size()){
		int l = min(x.size(),y.size());
		for(int i = 0;i < l;i++){
			if(x[i] != y[i]){
				return x[i] > y[i];
			}
		}
		return x.size() < y.size();
	}else{
		for(int i = 0;i < x.size();i++){
			if(x[i] != y[i]){
				return x[i] > y[i];
			}
		}
		return x[0] > y[0];
	}
}

int main(){
	int n;
	cin >> n;
	for(int i = 1;i <= n;i++){
		cin >> a[i];
	}
	sort(a + 1,a + n + 1,cmp);
	for(int i = 1;i <= n;i++){
		cout << a[i];
	}
	return 0;
}