#include<bits/stdc++.h>
using namespace std;
string s[25];
bool cmp(string s1,string s2){
    for(int i=0;i<min(s1.size(),s2.size());i++){
        if(s1[i]!=s2[i]) return s1[i]>s2[i];
    }
    if(s2.size()<s1.size()){
        return s1[s2.size()]>s2[0];
    }
    else{
        return s2[s1.size()]>s1[0];
    }
}
int main(){
    int n;
    cin>>n;
    //cout<<cmp("321","32")<<endl;
    for(int i=1;i<=n;i++){
        cin>>s[i];
    }
    sort(s+1,s+1+n,cmp);
    for(int i=1;i<=n;i++){
        cout<<s[i];
    }
    return 0;
}