#!/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 = ""
    max_len = sum([len(s) for s in strings])
    strings = [s + "🍣" for s in strings]
    for _ in range(max_len):
        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(["a", "bc"]) == "abc"
    # assert solve(["az", "aza", "azba"]) == "aaazazbaz"
    # assert solve(["ac", "bd"]) == "abcd"
    # assert solve(['one', 'two', 'three', 'four', 'five']) == "ffioneothreeturvewo"
    main()