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Timus Top Coders: Second Challenge

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G. Freedom of Speech

Time limit: 1.0 second
Memory limit: 64 MB

Background

The democracy is beautiful and perfect. It allows to resolve a lot of social problems via single universal method. First iteration - bomb a country. Second iteration - give some freedom for its people. The experts assert that it is cheaper to give them the freedom of speech. At least, they did so in Albania.

Problem

In Albanian, any expression is a sequence of words (it is not necessary for the words to be different), which are separated by delimiters - spaces, punctuation marks and so on. Notorious Albanian liberal Mohammed Tahir-ogly was absolutely sure that those delimiters bound the freedom of speech. He decided to carry out a language reform and get rid of the delimiters. After the reform is effected, any Albanian expression will be a sequence of unseparated words.
Famous Albanian conservative Ahmed Kasym-bey raised his voice against the reform. He pointed out, that after it some expressions with the same spelling, but formed by different sequences of words - and therefore with different meanings - may appear in Albanian. This ambiguity undoubtedly restrains the freedom of speech. Now Ahmed craves for finding at least one such expression to ruin the intentions of his political foe. He opened an Albanian dictionary, found exactly N different words S[i] in it and realized, that he could not manage this task alone.

Input

The first line contains the integer number N (1 ≤ N ≤ 100). Each of the next N lines contains a word S[i]. Each word consists of from 1 to 100 small latin letters.

Output

You should output "NO", if the desired expression does not exist. Otherwise the first line should contain "YES", and the second line should contain this expression. The expression should not be more than 20000 characters long. If the problem has several solutions, you may output any of them.

Sample

inputoutput
5
ab
acb
bc
abac
babbc
YES
abacbabbc

Notes

In the sample, the expression "abacbabbc" may be formed by the sequences of words "abac"+"babbc" and "ab"+"acb"+"ab"+"bc".
Problem Author: Nikita Rybak, Ilya Grebnov, Dmitry Kovalioff
Problem Source: Timus Top Coders: Second Challenge
To submit the solution for this problem go to the Problem set: 1455. Freedom of Speech