import heapq

class PriorityString:
    def __init__(self, s):
        self.s = s
    def __lt__(self, other):
        return (self.s + other.s) < (other.s + self.s)

n = int(input())
strings = [input().strip() for _ in range(n)]

heap = []
for s in strings:
    if s:
        heapq.heappush(heap, PriorityString(s))

result = []
while heap:
    current = heapq.heappop(heap)
    result.append(current.s[0])
    remaining = current.s[1:]
    if remaining:
        heapq.heappush(heap, PriorityString(remaining))

print(''.join(result))