n = int(input())
words = []
for i in range(n):
    words.append(input().strip())

ans = ''
while len(words) > 0:
    words.sort()
    if len(words[0]) == 1:
        s = words[0][0]
        tmpl = [w for w in words if w.startswith(s) and len(w) != 1]
        if len(tmpl) == 0:
            ans += s
            words.pop(0)
        else:
            tmpl1 = [w[1] for w in tmpl]
            if s < min(tmpl1):
                ans += s
                words.pop(0)
            else:
                ans += tmpl[0][0]
                words.remove(tmpl[0])
                words.append(tmpl[0][1:])
    else:
        ans += words[0][0]
        words[0] = words[0][1:]

print(ans)