#include<iostream>
#include<sstream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<string>
#include<vector>
#include<cmath>
#include<set>
#include<map>
#include<stack>
#include<queue>
#include<numeric>
#include<functional>
#include<complex>

using namespace std;
#define BET(a,b,c) ((a)<=(b)&&(b)<(c))
#define FOR(i,n) for(int i=0,i##_end=(int(n));i<i##_end;i++)
#define SZ(x) (int)(x.size())
#define ALL(x) (x).begin(),(x).end()
#define MP make_pair
#define FOR_EACH(it,v) for(__typeof(v.begin()) it=v.begin(),it_end=v.end() ; it != it_end ; it++)
typedef vector<int> VI;
typedef vector<VI> VVI;

int main()
{
    int n;
    cin>>n;
    vector<string> s(n);
    FOR(i,n) cin>>s[i];
    FOR(i,n) s[i] += "{";
    while(true){
        string less = "";
        int target = -1;
        FOR(i,n){
            if(s[i] == "") continue;
            if(less == "" || less > s[i]) {
                less = s[i];
                target = i;
            }
        }
        if(target == -1) break;
        char t = s[target][0];
        if(t != '{'){
            putchar(t);
        }
        s[target] = s[target].substr(1);
    }
    puts("");
    return 0;
}