def string_index(n, s_lst): res = [] for s in s_lst: copy_lst = s_lst.copy() copy_lst.remove(s) for i in range(1, len(s)): temp = s[:i] count = 0 for l in copy_lst: if temp != l[:i]: count += 1 if count == n - 1: res.append(temp) break return res if __name__ == "__main__": n = int(input()) s_lst = [] for i in range(n): s_lst.append(input()) res = string_index(n, s_lst) for s in res: print(s)