#include <iostream>
#include <algorithm>
using namespace std;
int main(){
    int n;
    cin>>n;
    string a[n];
    for (int i=0;i<n;i++){
        cin>>a[i];
    }
    sort(a,a+n);
    for (int i=n-1;i>=0;i--){
        cout<<a[i];
    }
    return 0;
}