Domino of words P47539

Statement

You are given $n$ words. Can you permute the words (not their letters) so that the second word begins with the last letter of the first word, the third word begins with the last letter of the second word, and so on?

Input

Input consists of several cases, each with $n$ , followed by $n$ words made up of between 1 and 10 lowercase letters. You can assume $1 \le n \le 10^5$ .

Output

For every case, print “yes” if it is possible arrange all the words like in the game of domino. Otherwise, print “no”.

Public test cases

Input

3 the easiest task
2 or not
1 hello
2 ab abc
5 za z zz zz bz
3 a a a

Output

yes
no
yes
no
yes
yes

Information

Author: Salvador Roura
Language: English
Official solutions: C++
User solutions: C++