#include <iostream>
#include <vector>
#include <map>
#include <algorithm>
using namespace std;

#define REP(i,s,e) for (i = s; i <= e; i++)
#define rep(i,n) REP (i,0,(int)(n)-1)
#define RREP(i,s,e) for (i = s; i >= e; i--)
#define rrep(i,n) RREP (i,(int)(n)-1,0)
#define INF (int)1e8
#define MOD (int)(1e9+7)

typedef long long ll;

int sp[50];
string s[50];

bool cmp(int x, int y) {
    int i = sp[x], j = sp[y];
    while (true) {
        if (i >= s[x].size())
            return false;
        if (j >= s[y].size())
            return true;
        if (s[x][i] < s[y][j])
            return true;
        else if (s[x][i] > s[y][j])
            return false;
        i++; j++;
    }
}

int main(void) {
    int i, n;
    cin >> n;
    rep (i,n) cin >> s[i];
    rep (i,n) sp[i] = 0;
    while (true) {
        char mn;
        int imn = -1;
        rep (i,n) if (sp[i] < s[i].size()) {
            if (imn == -1 || cmp(i,imn)) {
                mn = s[i][sp[i]];
                imn = i;
            }
        }
        if (imn == -1) break;
        cout << mn;
        sp[imn]++;
    }
    cout << endl;
    return 0;
}