Password Name Finder

Charlie is a skilled Internet user, and he proves it with the many email addresses he uses regularly. Each address is protected by a password. Because Charlie does not have a good memory, he invented a simple rule for making passwords that are easy to remember: each password is made by concatenating the names of two girls he secretly admires.

Charlie secretly admires at least two and at most five girls. Their names are all different, and each name consists of 3 to 8 lowercase English letters. Lucy knows Charlie's password rule and has found all of his passwords. Write a program that helps Lucy find the smallest possible set of names used to make the passwords.

The first line contains an integer N, the number of passwords (1 ≤ N ≤ 100).

Each of the next N lines contains one password. A password is a string of at most 16 lowercase English letters from a to z.

Print S, the minimum number of names that the passwords are made from, on the first line.

Then print the S names, one per line, in ascending lexicographic order.

The input is chosen so that the answer is unique.