#include <iostream>
using namespace std;

int main(void)
{
    int n;
    int smax = 0;
    string s[50];
    int index[50] = {0};
    cin >> n;
    for(int i = 0; i < n; i++) {
        cin >> s[i];
        smax += s[i].size();     
    }
    string res = "";
    for(int i = 0; i < smax; i++) {
        int buf[50];
        int len = 0;
        for(int j = 0; j < n; j++)
            if(index[j] < s[j].size())
                buf[len++] = j;
        for(int t = 0; t < 50 && len > 1; t++) {
            int nlen = 0;
            char mini = 127;
            for(int j = 0; j < len; j++) {
                int k = buf[j];
                if(index[k] + t >= s[k].size())
                    continue;
                int p = index[k] + t;
                if(s[k][p] < mini) {
                    buf[0] = k;
                    mini = s[k][p];
                    nlen = 1;
                }
                else if(s[k][p] == mini) {
                    buf[nlen++] = k;
                }
            }
            len = nlen;
            if(mini == 127)
                break;
        }
        res += s[buf[0]][index[buf[0]]];
        index[buf[0]]++;
    }
    cout << res << endl;
    return 0;
}