#include <cstring>
#include <iostream>
using namespace std;
int main(){
	char a[21][11];
	char sum[220]="";
	int n;
	cin>>n;
	
	for(int i=0;i<n;i++){
		cin>>a[i];
	}
	int js=1;
	char tmp[11]="";
	while(js!=0){
		js=0;
		for(int i=0;i<n-1;i++){
			if(strcmp(a[i],a[i+1])<0){
				strcpy(tmp,a[i+1]);	
				strcpy(a[i+1],a[i]);
				strcpy(a[i],tmp);
				js++;
			}
		}
	}
	for(int i=0;i<n;i++){
		strcat(sum,a[i]);
	}
	cout<<sum<<endl;
	return 0;
}