#include <bits/stdc++.h>

using namespace std;

string a[21] = {};

int main() {
    //输入+输出重定向
    freopen("../1269.txt", "r", stdin);
    int n;
    cin >> n;
    for (int i = 1; i <= n; i++) {
        cin >> a[i];
    }
    //排序
    sort(a + 1, a + n + 1, greater<string>());
    for (int i = 1; i <= n; ++i) {
        cout << a[i];
    }
    //关闭文件
    fclose(stdin);
    return 0;
}