def is_the_first_bigger(a, b):
    is_not_changed = True
    if len(a) > len(b):
        a, b = b, a
        is_not_changed = False
    if b[:len(a)] == a:
        a += b[0]

    return a > b and is_not_changed



def bubble_sort(a):
    curr_unsorted = len(a)
    while True:
        is_ordered = True
        i = 0
        while i + 1 < curr_unsorted:
            if is_the_first_bigger(a[i], a[i + 1]):
                a[i], a[i + 1] = a[i + 1], a[i]
                is_ordered = False
            i += 1
        if is_ordered:
            return
        else:
            curr_unsorted -= 1

N = int(input())
a = []
for i in range(N):
    a.append(input())
bubble_sort(a)
ans = ''
for i in range(len(a) - 1, -1, -1):
    ans += a[i]
print(ans)