import string

class StringMerge:
    def __init__(self):
        self.atoi = lambda a: ord(a)-ord('a') # alphabet to index
        self.endchar = chr(ord('z')+1)
        self.strmat = [[] for _ in range(len(string.ascii_lowercase))]

    def add(self, word):
        self._add(word+self.endchar)

    def _add(self, word):
        index = self.atoi(word[0])
        self.strmat[index].append(word)

    def merge(self):
        cur_top = 0 # init index = 'a'(=0)
        buff = []
        while cur_top < len(self.strmat):
            if len(self.strmat[cur_top]) > 0:
                self.strmat[cur_top].sort() # sorted by char e.g. fae,fab->x fab,fae->o
                tar = self.strmat[cur_top].pop(0)
                buff.append(tar[0])
                if len(tar) >= 3: # !! include endchar
                    # rest sub string, add
                    self._add(tar[1:])
                    # update top index
                    or_top = self.atoi(tar[1])
                    if cur_top > or_top:
                        cur_top = or_top
            else:
                # miss index, walk next
                cur_top += 1
        return ''.join(buff)

if __name__ == '__main__':
    n = int(input())
    sm = StringMerge()
    for _ in range(n):
        line = input()
        sm.add(line)
    print(sm.merge())