#!/usr/bin/python
# -*- coding: utf-8 -*-


def main():
    N = int(input())
    strings = []
    for _ in range(N):
        strings.append(input())
    results = solve(strings)
    print(results)


def solve(strings):
    t = ""
    for _ in range(sum([len(s) for s in strings])):
        min_string = min(strings)
        strings.remove(min_string)
        t = t + min_string[0]
        if len(min_string) > 1:
            new_string = min_string[1:] + "🍣"
            strings.append(new_string)

    return t


if __name__ == '__main__':
    # assert solve(["ac", "bd"]) == "abcd"
    # assert solve(['one', 'two', 'three', 'four', 'five']) == "ffioneothreeturvewo"
    main()