/* Author Name: Mohamed Elshenawy
 * Last Edit 31th Aug 2016
 * Largest Salary problem
 * This is the solution for Coursera Algorithm & Data sturcter course , Assignment for week 3 problem 6.
 */

#include <algorithm>
#include <sstream>
#include <iostream>
#include <vector>
#include <string>

using std::vector;
using std::string;

string largest_number(vector<string> a) {

	vector<int> numberTempo;
	std::stringstream ret;
	int i = 0 , lengthCount = 0 , numberNotSingle =0;
	for(i;i<a.size();i++){
		std::stringstream forNumber(a[i]);
		int numberInLoop;
		forNumber >> numberInLoop;
		if(numberInLoop < 10){numberTempo.push_back(numberInLoop);}
		else{
		// The next Line of Code is to split multiple number to single.
			for (; numberInLoop!=0;numberNotSingle = numberInLoop % 10 ,numberInLoop/=10,lengthCount++,numberTempo.push_back(numberNotSingle));
		}
	}
	std::sort (numberTempo.rbegin(), numberTempo.rend());
	for (size_t i = 0; i < numberTempo.size(); i++) {
		ret << numberTempo[i];
	}
	string result;
	ret >> result;
	return result;
}

int main() {
	int n;
	std::cin >> n;
	vector<string> a(n);
	for (size_t i = 0; i < a.size(); i++) {
		std::cin >> a[i];
	}
	std::cout << largest_number(a);
}